Solid Tumours Flashcards
What is the most common cancer wordlwide?
Female breast cancer
What is the incidence of breast cancer?
15% of all new cancer cases
Over 2.3 million new cases a year and 685,000 deaths.
What is the prognosis of breast cancer?
80.4% survive for 10 years or more
What is the average age of diagnosis of breast cancer?
63 years
What is the lifetime probability of developing invasive breast cancer for women?
12.3% or 1 in 7
What are the risk factors for breast cancer?
Age: >50
Personal history of breast or ovarian cancer
Family history of breast or ovarian cancer (HBOC)
Menstruation: Periods before age 12 and after 55
Pregnancy: Not being pregnant before age of 35
Hormone replacement therapy after menopause
Oral contraceptive
Radiation exposure at a young age
Lifestyle e.g. obesity, alcohol, food, exercise
What is atypical hyperplasia of the breast?
This diagnosis increases the risk of developing breast cancer in the future.
Typical ductal hyperplasia (ADH) differential diagnosis with ductal carcinoma in situ (DCIS)- same but smaller
What is Lobular carcinoma in situ (LCIS)?
LCIS refers to abnormal cells found in the lobules or glands of the breast. It is not considered cancer. However, LCIS in 1 breast increases the risk of developing invasive breast cancer in either breast in the future.
How does breast cancer present?
Most of the patients discover their disease in the context of routine screening.
The presence of breast lump, changes of breast shape or size, or nipple discharge should alert a woman. Mastalgia may also occur.
What are the two main types of breast cancer?
Breast cancer is characterized as noninvasive and invasive cancer mainly based on the location of the breast cancer cells i.e. if they are confined to the mammary ductal-lobular system or they have spread outside of the milk ducts or lobules into the surrounding breast tissue.
What is the most common non invasive breast cancer?
The most common noninvasive breast cancer type is DCIS, ductal carcinoma in situ, considered as Stage 0. It is graded as low, intermediate ad high based on the degree of differentiation of tumour cells.
What are the chances of DCIS progressing to invasive cancer?
There is at least 30% to 50% risk of untreated DCIS progressing to invasive carcinoma in the ipsilateral breast 10 to 20 years after initial diagnosis if no treatment applied. Therefore, surgical intervention to remove DCIS often followed by radiotherapy and/or medical treatment is highly recommended.
What are the types of invasive breast cancer?
Invasive or infiltrating ductal carcinoma- most common
Invasive lobular carcinoma (10% to 15% of all invasive breast cancers).
Less common invasive types are medullary, mucinous, tubular, metaplastic, papillary, micropapillary, apocrine and inflammatory breast cancer, an aggressive type (~1% to 5% of all invasive breast cancers).
What molecular markers are used to classify breast cancer?
Oestrogen recepter (ER)
Progesterone receptor (PR)
HER2
What is the significance or ER testing in breast cancer?
80% of breast cancer patients overexpress ER which drives the cancer
These patients are likely to respsonds to hormone therapy such as aromatase inhibitors and/or tamoxifen (SERM) which blocks oestrogen binding to ER
How are ER/PR/HER2 expression investigated?
IHC
Use the alfred score to determine if positive
HER2 is reflexed to FISH to confirm amplification if staining is greater than 2
What is the significance of PR testing in breast cancer?
65% of breast cancers are both ER and PR positive. PR is a target gene of ER and its expression is dependent upon oestrogen
ER/PR positive tumours respond better to ER modulator therapy (SERM)
PR positive breast cancers have a better prognosis
What is HER2?
ERBB2 part of the EGFR pathway
proto-oncogene
What is the significance of HER2 testing in breast cancer?
Overexpression of HER2 occurs in 15-20% of cancers and is associated with aggressive subtype and poor prognosis
Anti-HER2 herceptin is available as a treatment for these patients
What are HER2 low breast cancers?
Cancers assigned with low levels of HER2 protein and/or few copies of HER2 gene are sometimes now called as HER2-low. When categorizing breast cancer by HER2 expression, “HER2-low” cancers make up most cases. There has been promising results of targeted therapy with Tdx-D(Enhertu - trastuzumab deruxtecan
What is triple negative breast cancer (TNBC)?
TNBC accounts for 10-20% and lacks expression of all three receptors (ER, PR, and Her2). Thus, it cannot be treated using anti-estrogen hormonal therapies or trastuzumab (monoclonal antibody targeting HER2 protein). Associated with poorer prognosis
What mutations are found in TNBC?
- BRCA1 and 2/HRD: 10% germline BRCA and 35% other causes of HRD
- PIK3/AKT pathway
-Cell cycle checkpoints - Notch signalling
What potential targeted therapies are there for TNBC?
PARP inhibitors
PIK3CA inhibitors
Immunotherapy (PD-L1)
What is on the test directory for ER positive HER2 negative early breast cancer?
Gene expression assays: M3.2 OnocoType Dx, M3.3 EndoPredict, M3.3 Prosignia
What is the oncotype DX and why is it used in early stage ER+/HER- breast cancer?
21 genes analysed to predict chemotherapy benefit and prevent overtreatment of patients who do not need it
What is the significance of PD-L1 in breast cancer?
Atezolizumab is a PD-LA inhibitor that blocks the interaction between PD-L1 and PD-1, thereby promoting T cell activity.
PD-L1-positive patients with metastatic TNBC showed improved progression free survival (PFS) when pembrolizumab was given in combination with chemotherapy
What is the response rate for anti-PD-L1 therapy in breast cancer?
10-30%
Can have bad side effects including autoimmune disease
IHC of PD-L1 is used to determine who is likely to respond
What tests are on the test directory for breast cancer?
M3.5 NTRK testing
M3.6 PIK3CA
M3.7 DPYD
Oncotype
What is the clinical significance of PIK3CA on breast cancer?
Most recurrently mutated gene in breast cancer
Activating variants allows may respond to PIK3CA inhibitors- according to the SOLAR trial (11 specific variants but others may also respond)
What is the significance of ESR1 in breast cancer?
More common in metastatic cancers and associated with shorter progression free survival
They have been shown to be resistant to treatment with hormone therapies (AI, tamoxifen) but may respond to treatment with CDK4/6 inhibitors- clinical trials available
Elacestrant (a selective estrogen receptor degrader) has been FDA approved for ESR1 mutated breast cancers- NICE under development
What is the role of ctDNA in breast cancer?
Currently not on the test directory but likely to be added soon for ESR1
- ESR1 is a known acquired resistance mechanism to hormone therapies
- ctDNA would allow early detection of this resistance and variant is often not present in the primary tumour
- Potential access to other therapies such as Elacestrant
What is the significance of HRD in breast cancer?
It is derived by combining 3 main characteristics: numbers of telomeric allelic imbalances, large scale transitions, and loss of heterozygosity events (LOH), all of which are indicative of deficiency of the DNA repair system.
Predicts response to PARP inhibitors- currently in clinical trials BrightNess trial
How can breast cancer be monitored molecularly?
ctDNA Liquid biopsy blood test, for detecting the PIK3CA mutation, is approved by the FDA for breast cancer that can be used in clinical practice.
How is TNBC treated?
- Surgery/readiotherapy
- Chemotherapy
- Targeted: PIK3CA, NTRK, PARP, PD-L1
What are the ESMO guidelines recommendations for breast cancer treatment?
- Luminal A-like: endocrine therapy (ET) alone or with chemotherapy, in case of G3, T3 or ≥ 4 positive lymph nodes (IA)
- Luminal B-like (HER2-negative): ET and chemotherapy, but not concomitantly (IID)
- Luminal B-like (HER2-positive): chemotherapy and anti-HER2 (trastuzumab) and ET (IA). Only for selected cases, in which chemotherapy is contraindicated or refused by the patients, ET and trastuzumab may be considered as acceptable (VA)
- HER2-positive (non-luminal): chemotherapy and anti-HER2 (trastuzumab) (IA)
-Triple-negative (ductal): chemotherapy (IA)
What is the ESMO guidelines on breast cancer screening?
ESMO recommends periodically mammography screening for women between 50 and 69 years old (IA). More specific are the NICE and German guidelines which recommend mammography for women between 50 and 70 years old every 3 and 2 years.
ESMO also recommends yearly screening with MRI and mammography together or alternating every 6 months for women with a family history of breast cancer, starting 10 years prior to the diagnosis age of the earliest case in the family (IIIB).
What is the incidence of high grade serous ovarian cancer (HGSOC)?
Over 300,000 cases diagnosed worldwide per year, distribution varies internationally. Average 1.1% lifetime risk
6th most common cancer in women
What are the risk factors for ovarian cancer?
Family history
- First degree relative with breast/ovarian cancer, prostate cancer
- Ashkenazi Jewish heritage
Reproductive history
- Early menarche, late menopause, fewer pregnancies
- Pregnancy (before 25y), breastfeeding, late menarche, early menopause, contraceptive pill for 3+ years (↓ risk by 30-50%)
Obesity
Increasing age
Genetic predisposition
- Previous cancer such as breast
- Mutations in DNA damage repair (HRD, BRCA1, BRCA2)
Risk reduction
- Tubal ligation, prophylactic hysterectomy/salpingo/oophrectomy
What is the clinical presentation of ovarian cancer?
Patients may be asymptomatic or have non-specific symptoms that are related to involvement of abdominopelvic organs.
Currently no accurate medical screening available for early-stage detection
What is the prognosis of ovarian cancer?
- Only 20% diagnosed in early stages, when 5y survival is 94%
- 80% patients present with FIGO stage III or IV, leading to low median survival (5y <30%)
- Most reocur
What is HRD?
The inability to repair double stranded breaks by homologous recombination
This results in error prone DNA repair and genomic instability
How common is HRD in High grade serous ovarian cancer (HGSOC)?
Approximately 50% HGSOC harbour defects in HRR pathway genes
- most are either germline or somatic BRCA variants
- variants in other HRR genes e,g, RAD51D/D, BRIP1, RAD50, BARD1, CHEK2, MRE11A, NBN, PALB2- leads to a BRCA like phenotype
Outline the HRR pathway?
Requires recruitment of BRCA1 to double-stranded break (DSB), which then stimulates exonuclease-mediated 5’-3’ end resection to create single strand overhang.
RAD51-DNA filament is created by exchange of RPA for RAD51 by complex containing RAD51, PALB2 and BRCA2. Sister chromatid is used as a template for high-fidelity DNA repair.
What percentage of HGSOC have BRCA variants?
Pathogenic variants are early events in ~20% cases (account for most dHRR), consisting of germline in ~15% HGSOC patients and somatic in ~6-7% HGSOC cases
What are reversion mutations in BRCA?
Reversion mutations in the BRCA genes that can reinstate homologous recombination proficiency (HRP) (i.e. cells/tumour cells are able to effectively repair DNA damage by HRR) have also been identified. This is often associated with primary or acquired Fce to PARP inhibitors, topoisomerase inhibitors or platinum salt
What other genes have clinical relevance in ovarian cancer?
TP53
- >95% HGSOC present TP53 variants early in oncogenesis and contribute to genomic instability
SMARCA4
- present in small cell carcinoma of the ovary
DICER1
- Seen somatically in ~50% of SLCT and at younger patient age and with moderately/poorly differentiated tumours
FOXL2
- c.402C>G, p.(Cys134Trp)-mutant
- Nearly all adult granulosa cell tumours
CTNNB1 and APC
- Variants in most microcystic stromal tumour (MCST)
What testing is on the test directory for ovarian cancer?
M2.1: BRCA1/BRCA2, SMARCA4
M2.3: NTRK
M2.5: HRD
M233.1: WGS
M245.1: ovarian sex cord stromal tumours- FOXL2, CTNNB1, APC, DICER1
R207: germline SNV and CNV- BRCA1; BRCA2; BRIP1; MLH1; MSH2; MSH6; PALB2; RAD51C; RAD51D
How is ovarian cancer diagnosed?
Physical exam
Imagining: Transvaginal ultrasound, CT and chest X ray
Biochemistry: elevated serum CA125 (>35 units/mL but non specific)
Histology: pleomorphic nuclei, high mitotic activity, necrosis, multi-nucleated cells common, prominent lymphocytic infiltrate.
What IHC is used to diagnose HGS ovarian cancer?
~90% demonstrate nuclear WT1,
~95% abnormal p53 (strong diffuse staining in >80% cells, or no staining), CK7/CA125/PAX8 typically positive
ER often expressed, p16 (CDKN2A) strong diffuse staining in ≥50% tumours,
PTEN and ARID1A retained.
These are useful in differentiating HGSOC from emdometroid
What is mainstreaming?
All ovarian and breast cancer patients are eligible for germline BRCA testing directly from oncologists to allow for treatment with PARP inhibitors
When is somatic BRCA testing required in ovarian cancer?
Tumour molecular testing recommended by NCCN after primary surgery or at recurrence/persistence if not performed at this timepoint, to inform utility of PARP inhibitors
Is ovarian cancer monitored?
Monitoring not currently performed through molecular testing equally across the U.K., CA125 routinely reviewed, however ctTNA is a focus of development for NHSE across solid tumours.
What is the NICE recommendation for treatment of stage 1 ovarian cancer?
- Optimal surgical staging (TAH, BSO, infracolic omentectomy, bx of peritoneal deposits)
- Platinum based chemotherapy- adjuvant chemo (6 x carboplatin) for high-risk Stage I (G3, or Ic) not low-risk (G1/2, Ia/b)
What is the treatment of stage II-IV ovarian cancer?
- Surgical objective to complete resection of all macroscopic disease
- Intraperitoneal chemotherapy only as part of a clinical trial
- Chemotherapy
How is recurrent ovarian cancer treated? (or maintenance therapy)
PARP inhibitors (dependent on BRCA and HRD status)
- Niraparib/rucaparib maintenance +/- after 1st line PBCT (2+ courses)
- Olaparib maintenance through CDF for FIGO 3/4 after complete/partial response to 1st line PBCT+bev and is HRD+
+/- bevacizumab
What are PARP inhibitors?
- PARP is required in the Base Excision Repair pathway, inhibition of which causes an accumulation of DSB
- Patients with deficient HRR are unable to HiFi repair DSBs, which accumulate and catastrophic DNA damage and cell death
- This leads to Synthetic lethality
- Most benefit derived from 1st line PBCT leading to SSB/DNA damage, then PARPi to inhibit mechanism of repair
What guidelines are used in ovarian cancer?
NICE
ESMO-ESGO consensus recommendations
- recommends BRCA germline and somatic testing and HRD testing to identify patients who would respond to PARP inhibitors for maintenance therapy after platinum based chemo
What is the prostate?
The prostate is a male sex glandular structure
Its main functions are to provide force to ejaculate semen and to add nutrient-rich alkaline fluid to the semen to maintain spermatic health post-ejaculation and enhance fertility
What is the process of malignant transformation of the prostate?
Malignant transformation of the prostate follows a multistep process, initiating as Prostatic Intraepithelial Neoplasia (PIN) followed by localized prostate cancer and then advanced prostate adenocarcinoma with local invasion, culminating in metastatic prostate cancer.
PIN can be divided into two grades, low (LGPIN) and high (HGPIN). HGPIN has a high predictive value for predicting progression to adenocarcinoma.
What is the incidence of prostate cancer?
1 in 6 men in the UK will be diagnosed with prostate cancer in their lifetime.
In the UK, it is the most common malignancy in men with around 52,000 diagnosed with prostate cancer each year.
What are the risk factors for prostate cancer?
- Age
- Black ethnicity
- Family history
- Obesity
How does prostate cancer present?
Often asymptomatic
- Lower Urinary Tract (LUT) symptoms (e.g. nocturia, frequency, hesitancy, urgency or retention)
- Visible Haematuria
- Abnormal Digital Rectal Examination (DRE)
- Symptoms of advanced disease (lower back pain/bone pain secondary to bony metastasis, weight loss
What fusion is present in up to 50% of prostate cancers?
The TMPRSS2-ERG fusion plays a significant role in the occurrence and progression of approximately 50% of prostate cancers. This fusion involves the E-26 transformation-specific (ETS)-related gene (ERG) and the transmembrane serine protease 2 (TMPRSS2).
TMPRSS2-ERG regulates androgen receptor (AR) signalling
Is there targeted treatments available for prostate cancers with TMPRSS2-ERG fusions?
Enzalutamide, inhibits androgen, is more effective in cells or tumors with TMPRSS2-ERG translocations. These tumors exhibit increased AR signaling, making them more responsive to enzalutamide treatment
Investigation into targeted therapies is ongoing
What targets are covered on the test directory for prostate cancer?
BRCA1, BRCA2
TMPRSS2-ERG
NTRK1/2/3
Why is BRCA tested in prostate cancer?
Both somatic and germline BRCA variants have been reported in prostate cancer
These patients are eligible for treatment with Olaparib. Testing on somatic tissue should be done first and then blood if tissue not available (R444)
What is the diagnostic pathway for prostate cancer?
According to ESWMP guidelines
GP
- a digital rectal examination (DRE)
- a Prostate Specific Antigen (PSA) blood test
Imaging
- If elevated PSA, MRI
If positive
- transrectal ultrasound-guided (TRUS) biopsy
- histology, grade, stage and risk stratification
What is PSA?
Prostate Specific Antigen (PSA) is a protein produced by prostate epithelial cells. PSA is produced by normal prostate tissue, however levels in the blood tend to increase in malignancy. It may be used both in the diagnosis and surveillance of prostate cancer but is not perfect- threshold still in discussion
Is there a screening programme for prostate cancer?
No
There have been a number of studies that have tried to establish if a screening programme would be an overall benefit to the population.
PSA testing is used sometimes but has a high false positive rate. PSA testing can be discussed with men over 50, and should be offered to those men over 50 who request it.
How is prostate cancer staged?
TNM
using the 2018 classification for adenocarcinoma of the prostate based on primary tumour (T), lymph node involvement (N) and metastases (M)
How is prostate cancer graded?
The Gleason score is a histological grade assigned to prostate cancers. From the biopsy, the most common and second most common tumour pattern is assigned a score of 1 to 5 (5 being the highest grade) to give a combined score of 2 to 10.
Grade 1 (score of 6): Cells look simialr to normal prostate cells
Grade 5 (score 10): Cells look very abnormal
How is prostate cancer stratified based on risk?
Using the Cambridge Prognostic Group (CPG) as low, intermediate and high on the basis the PSA, Gleason score and clinical stage.
How is low risk prostate cancer treated?
- Active surveillance: an option in low-risk localised prostate cancer. It involves regular PSA measurements, digital rectal examinations and multiparametric MRIs. It is used as many with low-risk localised disease will have years without disease progression.
- Radical prostatectomy: is a definitive treatment option for localised prostate cancer. It involves the removal of the entire prostate gland and surrounding tissues.
- Radical radiotherapy: is a definitive treatment option for localised prostate cancer. May be combined with brachytherapy (implanting radioactive seeds directly in the prostate)
How is intermediate risk prostate cancer treated?
- Androgen-depravation therapy: this treatment aims to lower androgen levels (most common)
- Gonadotropin-releasing hormone (GnRH) agonist: cause a ‘chemical castration’. Goserelin is a commonly used GnRH agonist
- Bicalutamide (an anti-androgen)
- Bilateral orchidectomy (castration)
How is high risk prostate cancer treated?
- Neoadjuvent chemotherapy (Docetaxel)
- Radiotherapy
- Radical prosteoectomy
How are relapsed prostate cancer patients treated?
Olaparib is NICE recommneded for relapsed BRCA positive prostate cancer patients
What is endometrial carcinoma?
Endometrial cancer arises from the epithelial lining of the uterus. Historically classified into two classes
1.Hormonally dependent (Indolent, low grade, endometrioid carcinomas)
2.Hormonally independent – (associated with poorer prognosis, non-endometrioid – serous and clear cell morphology, clinically aggressive, that are unrelated to oestrogen stimulation).
What are the four classes of endometrial cancer according to The Cancer Genome Atlas (TCGA), ?
- Group 1, with POLE mutations, is associated with a good prognosis.
- Group 2, with MMR deficiency, is associated with an intermediate prognosis.
- Group 3, showing low–copy-number alterations, is also associated with an intermediate prognosis.
- Group 4 tumours, with high–copy-number alterations and TP53 mutations are associated with a poor prognosis.
What is the incidence of endometrial cancer?
3.4% of all new cancers
Most common invasive cancer of female genital tract
What is the prognosis of endometrial cancer?
81% 5 year survival rate
How does endometrial cancer present?
- The first sign is most often vaginal bleeding not associated with a menstrual period.
- Pain with urination,
- Pain during sexual intercourse,
- Pelvic pain
What are the risk factors for endometrial cancers?
- Obesity (In postmenopausal women, there is greater synthesis of oestrogens in body fat)
- Diabetes (abnormal glucose tolerance is found in more than in 60%).
- Hypertension
- Infertility
- Women with oestrogen secreting tumours have a higher risk of endometrial cancer.
- Endometrial cancer is extremely rare in women with no ovaries
What are the types of endometrial cancer?
Endometrioid carcinoma
Serous carcinoma
Clear cell carcinoma
Undifferentiated carcinoma
Mixed carcinoma
Other
Carcinosarcoma
How is endometrial cancer graded?
FIGO criteria
- Non-gladular, non squamous growth and cytological atypia increases grade
What IHC markers are used to identify endometrial carcinoma?
Low grade
- ER/PR, p16
High grade
- ARID1A, PTEN, MMR, p53
What is serous endometrial carcinoma?
Serous carcinomas represent approximately 10% of all endometrial carcinomas but account for as many as 40% of endometrial cancer–related deaths.
The presence of TP53 is supportive of serous carcinoma.
What is the function of POLE?
Polymerase δ (pol δ) and Polymerase ε (pol ε) are the principal DNA replicases in eukaryotic cells.
-They are coded for by the genes POLD1and POLE
- Pol ε ensures accurate synthesis of the leading strand during DNA replication and is involved in proof reading and error correction
What is the affect of POLE LOF variants?
Loss of proofreading, catalytic and error-correction during DNA replication that results in an ultramutational state, leading to the accumulation of mutations in the genome
What is the frequency of POLE variants in endometrial carcinoma?
7-12% have variants in exonuclease domain
What variants are known in POLE?
11 distinct pathogenic variants have been classified
- accounts for 2/3s of POLE mutant EC
What is the MMR system?
- Identifies and corrects base-base mismatches and insertions/deletions
- Reduces replication-associated errors and contributes to cell cycle arrest and programmed cell death
- Defects in MMR increase spontaneous mutation rate
- Leads to mutagenesis in the short term and tumorigenesis in the long term
How is MMR endometrial cancer group identified?
IHC for MMR genes
- complete loss of one or one heterodimer of MMR
e.g. MLH1 and PMS2 or MSH2 and MSH6
What testing does WHO 2022 recommend for classification of endometrial cancer?
Reflex testing if negative in the following order:
1. POLE status (NGS)
2. MMR (IHC
3. P53 status (IHC, if inconclusive than NGS)
NGS for TP53 is much more accurate than IHC
Why is it important to determine the molecular subtype of endometrial cancer?
- Groups are prognostically distinct
- Groups exhibit characteristic responses to therapy that are not captured in existing treatment algorithms- POLE mutated patients are being overtreated
- Certain groups are associated with hereditary cancer syndromes (MMR-d and Lynch Syndrome; p53-mut and BRCA1 and BRCA2) – role in screening and prevention
What does NICE recommend about MMR testing in endometrial cancer?
All endometrial cancers are MMR tested using IHC
- if loss of expression of MLH1/PMS2 then reflex for MLH1 promoter hypermethylation as most common cause of somatic loss
- If negative, refer to clinical genetics and send for germline MMR testing
What is the incidence of colorectal cancer?
42,896 new cases each year
16,808 deaths
6-7% lifetime risk
What is the prognosis of colorectal cancer?
53% >10 year survival
What are the risk factors for colorectal cancer?
- Older (age-specific incidence rates increase steeply after age 50, with the highest rates above age 85 years)
- Male (RR~1.83)
- Family history of CRC
What is the clinical presentation of colorectal cancer?
- Change to bowel habits
- Loose poo or diarrhoea outside normal for person pattern
- Constipation outside normal for person pattern
- Blood in poo
- Increased frequency of passing stools/ increased urge to pass stool.
- Abdominal pain
- Abdominal bloating
- Losing weight without trying
- Feeling unusually tired
What are the WHO classification of colorectal cancers?
Adenocarcinoma
Mucinous
Signet ring cell carcinoma
Squamous cell carcinoma
What is the diagnostic pathway for colorectal cancer?
Colonoscopy
Biopsy
Imaging
ESMO, NICe
What IHC markers are used to identify colorectal cancer?
Cytokeritin 20+
Cytokeritin 7-
CDX2+
What somatic testing is included in the test directory for colorectal cancer?
M1.1- KRAS, NRAS, BRAF
M1.4- MSI
M1.5- MLH1 promoter hypermethylation
M1.6- NTRK1/2/3
M1.9- MLH1, MSH2, MSH6, PMS2, POLE, POLD1 (somatic lynch)
Why are KRAS and NRAS targets for colorectal cancer?
- Activating variants in KRAS and NRAS result in constitutive activation of the RAS/RAF/MEK/ERK pathway.
- CRC would be eligible for treatment with anti-EGFR therapy e.g. cetuximab or panitumumab.
- KRAS/NRAS are downstream of this point to inhibition via anti-EGFR therapy would be ineffective.
- intermediate prognosis
Why is BRAF testing carried out in colorectal cancer?
BRAF variants are present in approx 5-10% of CRC cases
Associated with:
- Right side tumours
- Older age
- Female
- MSI-high
Activating variants in BRAF result in constitutive activation of the RAS/RAF/MEK/ERK pathway and will not respond to anti-EGFR therapy
- BRAF V600E carrying CRC can access treatment with encorafenib plus cetuximab per licensing agreement.
What is the prognosis significance of BRAF in colorectal cancer?
Prognostic marker:
- poor prognosis if present in microsatellite stable tumour
- good prognosis if present in microsatellite unstable tumour
Why is MMR IHC carried out on all colorectal cancers?
NICE improving outcomes recommends
- Loss of MMR is indicative of lynch syndrome and starts the lynch reflex pathway
What is the prognostic significance of MMRd colorectal tumours?
Improved prognosis and good response to immunotherapy
Poor response to 5 FU chemotherapy
What pathway is used if MMRd is identified?
Wither IHC or MSI used to identtify potential lynch cases
- MLH1 promoter hypermethylation
- BRAF V600E testing- somatic marker
- Germline testing
- Somatic lynch testing if still no cause identified
Why is microsatellite testing used in colorectal cancer?
- When repair pathways are dysfunctional then there can increased instability at repetitive regions of the genome.
- Microsatellite can be assessed for integrity – please review other notes for details.
- Microsatellites that show variations in size and slippage indicate that the repair pathways in a tumour have been disrupted and the patient may have Lynch syndrome or somatic Lynch-like syndrome.
Why is MLH1 promoter hypermethylation used in colorectal cancer?
Colorectal and endometrial cancers are all screened by IHC to identify cases showing loss of expression of mismatch repair proteins (MLH1, MSH2, MSH6 and PMS2)
Loss of MLH1 and PMS2 is more commonly due to sporadic events so further testing is required to investigate these IHC results.
MLH1 promoter hypermethylation testing will identify cases where hypermethylation the promoter region prevents expression of MLH1.
This is usually due to hypermethylation in the tumour genome but on occasion germline constitutional hypermethylation of MLH1 promoter has been observed.
Why are MMR, POLE and POLD1 (M1.9) tested in the tumour of colorectal cancer?
Look for the somatic second hit in a Lynch syndrome patient’s tumour
Two somatic pathogenic variants to explain IHC expression loss in a tumour when germline showed no evidence of Lynch syndrome
How is localised colorectal cancer treated according to NICE?
Surgery + neoadjuvent therapy
If MMR-P- 5-FU
If MMR-d- Capectiabine
How is metastatic CRC treated according to NICE?
MMR-P
- Adjuvent chemotherapy and anti-EGFR therapy
MMR-D
- Adjuvent chemotherapy and anti-EGFR therapy
- immunotherapy)
KRAS/NRAS mut and MMR-p
- adjuvent chemo
KRAS/NRAS mut and MMR-d
- Adjuvent chemo and immunotherapy
BRAF
- BRAF inhibitor plus anti-EGFR
What are the main classifications of lung cancer?
Small cell lung cancer (SCLC) - 15%
Non-small cell lung cancer (NSCLC) – 85%
- Adenocarcinoma
- Squamous cell carcinoma (SCC)
- Large cell neuroendocrine
What is the incidence of lung cancer?
5-10 per 100K in never-smokers, 20-30x as high in smokers
According to the World Health Organization (WHO), lung cancer accounted for 11.4% of all new cancer cases in 2020
What are the risk factors for lung cancer?
- Smoking
- Radon exposure
- Occupational agents (asbestos, aluminium production, arsenic, coal, dioxin, radiation etc)
- Air pollution
- Family history
- Personal history of lung disease- e.g. COPD
How does lung cancer present?
> 80% present with locally advanced or metastatic disease
Primary tumour
- Persistent cough,
- Haemoptysis (coughing up blood),
- Dyspnea (shortness of breath),
- Chest pain
Metastasis
- Headache/seizures
- Bone pone
- Weight loss
- Fatigue
How is lung cancer diagnosed?
Imaging
- Chest X ray followed by PET, CT
Biopsy
-Histological subtyping and TNM staging
- IHC used
What IHC markers are used to histologically subtype SCLC?
Cytokeratin AE1/3 +
TTF1 +
Synaptophysin +
CD56 +
Napsin A and p40 -
What IHC markers are used to histologically subtype lung adenocarcinoma?
Cytokeratin AE1/3 +
TTF1 +
Napsin A +
Synaptophysin -
CD56 -
p40 -
What IHC markers are used to histologically subtype lung squamous cell carcinoma?
Cytokeratin AE1/3 +
p40 +
TTF1 -
Napsin A -
Synaptophysin -
CD56 -
How is SCLC treated?
Stage 1: Surgery and adjuvent chemo/radiation
Stage 2-4: incurable, no targeted therapies
What is the characteristic tumour profile of SCLC?
TP53 and RB1 LOF
High TMB
Associated with heavy smokers so G>T and C>A transversions
High number of CNVs
What are the SCLC test directory targets?
RB1 CNV: used in equivocal cases to aid diagnosis and to identify possible resistance mechanism to chemotherapy
NTRK fusions: treatment eligibility
How is stage 4 NSCLC treated?
Incurable so treated with systemic therapies
- Based on the presence of targeted therapy and PD-L1 expression
- If <50% PD-L1: platinum based chemo +/- pembrolizumab
- if >50% PD-L1: pembrolizumab +/+ pemetrexed and carboplatin
- if targeted event
What test directory targets are there for NSCLC?
SNV: EGFR, KRAS, BRAF, MET, ALK
CNV: MET
Structural: ALK, ROS1, RET, NTRK1, NTRK2, NTRK3
ctDNA: EGFR, ALK
What is the frequency, common mutations and clinical relevance of EGFR variants in NSCLC?
- 10-15%
- Activating missense variants e.g. L858R, deletion in exon 19 and insertions in exon 20
- Predicts response to EGFR TKI’s
What acquired resistance mechanisms are seen in EGFR treated NSCLC?
EGFR variants e.g. T790M, C797S
MET amplification
What EGFR TKIs are used to treat NSCLC?
Erlotinib and Gefitinib
- First-generation EGFR inhibition
- Most common resistance mechanism is Thr790Met in exon 20
Afatinib, Dacomitinib
- Second-generation ERBB family blockade
Osimertinib
- Third-generation, targets T790M
- Most common EGFR-based resistance mechanism is Cys797Ser in exon 20
What is the clinical significance of EGFR exon 20 insertion in NSCLC?
Will not respond to standard EGFR TKIs
Mobercertinib
- TKI specific for EGFR exon 20
-Now removed from NICE commissioning due to adverse affects
Amivantamab
- Monoclonal antibody for EGFR exon 20
- Licensed but not yet NICE recommended, may access through special circumstances
What is the frequency, common mutations and clinical relevance of KRAS variants in NSCLC?
25%
SNVs and indels affecting G12 and Q61
Poor prognosis and G12C predicts repsonse to KRAS G12C specific TKIs
- Co-occurring TP53 associated with increased immunotherapy response
What targeted treatments are available for KRAS mutated NSCLC?
KRAS notoriously difficult to target therapeutically
Sotorasib
- G12C specific
- Available through CDF
- Second line treatment
What treatments are available for BRAF mutated NSCLC?
Only for Class 1 V600 variants
Dabrafenib plus trametinib (BRAF/MEK combination therapy)
What is the frequency, common mutations and clinical relevance of BRAF variants in NSCLC?
1-2%
Three classes of BRAF variants
- Class 1: V600 variants
- Class 2: Non-v600 variants, activating
- Class 3: Kinase dead
Class 1 BRAF variants are associated with poor prognosis and lower response to immune checkpoint inhibitors but response to BRAF.MEK inhibition
What is the frequency, common mutations in MET variants in NSCLC?
3-4% Splicing (exon 14 skipping)
2-4% Amplification
What is the clinical significance of MET exon 14 skipping variants in NSCLC?
Predicts response to MET TKI- Tepotonib
What is the clinical significance of MET amplification in NSCLC?
Secondary MET amplification is associated with acquired resistance to EGFR TKI
Can also be primary oncogenic event
No NICE approved therapy but some evidence of response to criztonib
How are MET variants detected?
Exon skipping
- DNA splicing variants
- RNA exon skipping
- between 60-90% concordance in DNA but RNA is gold standard
Amplification
- NGS CNV calling
- FISH (confirmation)
What is the frequency, common mutations and clinical relevance of ALK variants in NSCLC?
ALK Fusions e,g, ELM4-ALK (3-7%) inv(2)(p21;p23)
Predicts response to ALK inhibitor therapy- rapid response
What treatments are available for ALK rearranged NSCLC?
Crizotinib
- First generation
- Approved for first and second line
Certinib and Alectinib
- Second generation
Lorlatinib
- Third generation
- Sensitive to ALK resistance mutations including G1202R
- no longer approved first-line (July 2023), second line only
What resistance mechanisms are there to ALK TKIs in NSCLC?
ALK SNVs e.g. G1202R, L1196M
ALK amplification
MET amplification
Different mechanisms of resistance may be sensitive to different lines of treatment
What is the frequency, common mutations and clinical relevance of RET variants in NSCLC?
RET fusions 1%
KIF5B-RET, CCDC6-RET
Response to Selpercatinib
What is the frequency, common mutations and clinical relevance of ROS1 variants in NSCLC?
ROS1 Fusions 2%
CD74-ROS1
EZR-ROS1
Response to Crizotinib
- ROS1 and ALK share 49% amino acid sequence homology so crizotinib can bind to both
What is the frequency, common mutations and clinical relevance of NTRK variants in NSCLC?
NTRK fusions 1%
LMNA-NTRK1
ETV6-NTRK3 t (12; 15) (p13; q25)
Response to Larotrectinib and Entrectinib
- Available once all treatment options have been exhausted
What other non-TD targets are used in NSCLC?
ERBB2
- Response to ERBB2 TKI’s
- Amplification is a resistance mechanism to EGFR TKI
PIK3CA
- response to targeted therapy
TP53
- increased response to immune checkpoint
How are structural variants detected in NSCLC?
RNA sequencing panels
FISH
IHC
What is the role of ctDNA in NSCLC?
EGFR and ALK ctDNA currently on the test directory
- Currently delivered by a national 2-hub model for NSCLC
- Can be used when a tumour is inaccessible to biopsy
- Potential disease monitoring mechanism and potentially identify resistance variants prior to disease progression
- More representative picture of the tumour heterogeneity.
What is the prognosis of lung cancer?
NSCLC: 5-year survival 5%
SCLC: 5 year survival at 2%
What guidelines are used in NSCLC?
NICE
ESMO
What is melanoma?
Melanoma arises from an accumulation of mutations that transforms melanocytes, most commonly in the skin.
How is melanoma classified according to the WHO?
Melanoma arising due to UV radiation
- Low-CSD (cumulative sun damage) melanoma- superficial spreading melanoma
- high-CSD melanoma- Lentigo maligna melanoma , Desmoplastic melanoma
Melanoma not associated with CSD
- Spitz
- Acral
- Mucosal
-Uveal
- Melanoma arising within blue naevi
- Melanoma arising in congenital naevi
Nodular Melanoma
How does melanoma evolve from a benign naevus?
Benign naevus
- Harbours only a single mutation and no other pathogenic alterations
- e.g. BRAF V600E
Melanocytoma
- Evolved from benign naevi with additional pathogenic mutations but have not yet reached malignant state
Malignant melanoma
- acquired additional pathogenic mutations and becomes malignant
What is the incidence of melanoma?
5th most common cancer- 4% of all new cancer cases
Adult incidence: 20 million cases per year
What are the most common melanoma in different populations?
Caucasain: superficial spreading
Asian, hispanic and African- Acral melanoma
What are the risk factors of melanoma?
86% of cases are preventable
- Fitzpatrick skin type 1: never tans (always burns), fair skin, blue eyes, red/blond hair, freckles
- history of blistering sunburn
- genetic predisposition
- immunosupression
- Congenital nevi
- Environmental factors (tanning beds, sun exposure)
How does cutaneous melanoma present?
New/changing pigmented skin or mucosa lesions. Lesions may be crusting, itching and may bleed.
ABCDE model
A - Asymmetry: Asymmetric in shape, size, or color.
B - Border Irregularity: The edges of the mole or lesion are irregular, ragged, notched, or blurred, rather than smooth and well-defined.
C - Colour Variation: The mole or lesion exhibits uneven colouring or multiple colours
D - Diameter: >5mm or is increasing in size over time.
E - Evolution: The mole or lesion has undergone changes in size, shape, colour, or texture over time, or new symptoms such as itching, tenderness, or bleeding have developed
What test directory targets are there for melanoma?
SNVs: BRAF, NRAS, KIT
Structural: NTRK1/2/3
CNVs: MYB, RREB1, CCND1, MYC, CDKN2A- for equivocal cases
What is the frequency, common mutations and clinical relevance of BRAF variants in melanoma?
50% - most commonly superficial spreading melanoma
BRAF V600 are the most common
Associated with aggressive disease and makes patient eligible for NICE approved targeted therapy BRAF/MEK combination therapy (only V600 variants): Dabrafenib+Trametinib/ Encorafenib+binimetinib
What is the frequency, common mutations and clinical relevance of NRAS variants in melanoma?
15-20% of melanoma
NRAS Q61 are the most common, typically mutually exclusive with BRAF V600
Associated with aggressive disease
There is no targeted treatment but there is some evidence that patients may respond to MEK inhibitors
What is the relevance of concurrent NRAS and BRAF variants in melanoma?
NRAS variants can be found with Class 3 BRAF variants. This results in elevated oncogenic potential through activation of the MEK/ERK pathway and these tumours may be more likely to respond to MEK inhibitors.
What is the frequency, common mutations and clinical relevance of KIT variants in melanoma?
Present in 10.8% of melanomas, most commonly high CSD (Lentigo maligna melanoma)
Targeted treatment: Fair responses to TKIs such as imatinib and sorafenib but this is not licensed
What is the frequency, common mutations and clinical relevance of NTRK variants in melanoma?
NTRK fusions are present in <1% cutaneous/mucosal melanoma but 20-30% spitzoid melanomas
ETV6:NTRK3 t(12 15)(p13 q25)
Can aid in diagnosis of spitzoid neoplasm
NICE approved targeted treatment available for these patients- NTRK inhibitors Larotrectinib and entrectinib- only once all treatment options have been exhausted
What TD targets are there for uveal melanoma?
BRAF, NRAS, NF1
What is the frequency, common mutations and clinical relevance of NF1 variants in melanoma?
10-15% of melanomas
LOF variants in NF1 are particularly common in lentigo maligna melanoma.
Associated with very high TMB
Not a test directory target for melanoma but there is some preclinical evidence that these patients may respond to MEK inhibition.
What are the common mutations and clinical relevance of GNAQ and GNA11 variants in melanoma?
Codon Q209 hotspot variant dominates Uveal (and Blue Neavi) melanoma, whilst BRAF V600 is unusual in this subtype
Some response to MEK inhibitor, but no improvement in overall survival
What is the frequency, common mutations and clinical relevance of BAP1 variants in melanoma?
3-4% ocular melanoma
PARP inhibitors being explored for these patients
Germline variants associated with BAP1 predisposition syndrome
Associated with greater metastatic disease potential
What is the frequency, common mutations and clinical relevance of TERT promoter variants in melanoma?
43% melanomas, especially non-acral skin
Associated with older age, sun exposure, thicker tumours, BRAF variants
Most common in superficial spreading
Associated with poorer prognosis
What molecular analysis can be used to help diagnose equivocal melanocytic lesions?
Copy number panel either using array or FISH
- RREB1
- MYB
- CCND1
- C-MYC
- CDKN2A
- Centromere 6
This is particularly useful when diagnosing spitz melanoma which can be diagnostically challenging to distinguish Spitzoid melanoma from benign Spitzoid melanocytic lesions
What is TMB?
Tumour Mutation Burden (TMB)
The total number of somatic/acquired mutations per coding area of a tumour genome (Mut/Mb).
Why is TMB important in melanoma?
Melanoma is known to have some of the highest TMB scores compared with other solid tumour types.
TMB however varies within melanoma subtypes, with NF1 mutated and High CSD cutaneous melanoma having the highest TMB
High TMB is a positive predictor of response to immunotherapy with checkpoint inhibitors such as anti-PD1 (nivolumab, pembrolizumab) and anti-CTLA4 (ipilimumab),
Not all high TMB tumours will respond to immunotherapy
How is melanoma diagnosed?
Imaging
Sentinel lymph node biopsy
Scar re-excision
Histology to subtype and stage
IHC for protein overexpression or loss of expression, e.g p16 (CDKN2A)
Equivacol cases: FISH, SNP arrays or NGS to detect a CNV ‘melanoma pattern’ or variants that may inform on subtypes.
What IHC is used in the diagnosis of melanoma?
S100
MelanA
HMB45
SOX10
How is melanoma staged?
TNM: tumour nodes metastases
T: Breslow thickness (depth of tumour in mm from skin), Ulceration
N: Largely based on number of involved nodes
M: Location of distant metastases
How is melanoma prognosis determined?
Stage
Serum LDH
BAP1 loss/monosomy 3 is poor prognosis in uveal melanoma
BRAF/NRAS poor prognosis
How is localised melanoma treated?
Surgical removal/resection, with or without radiotherapy (depending on histological types and resection margins)
Sentinel lymph node biopsy is recommended for Breslow thickness of >1mm, ulcerated thinner melanoma may also be indicated for SLNB
How is metastatic melanoma treated?
Stage III
Surgical resection followed by PD-1 inhibitor OR
BRAF plus MEK inhibitor in V600 mutant melanoma
Lymphadectomy of involved LN if benefit is likely to outweigh the significant rate of morbidity associated with this procedure
Unresectable III and untreated stage IV
Checkpoint inhibitor combination therapy Pembrolizumab, Nivolumab (anti-PD-1); Ipilimumab (anti-CTLA-4))
BRAF plus MEK inhibitor if immunotherapy unsuitable or rapid progression/high disease burden) - Dabrafenib+Trametinib/Encorafenib+binimetinib;
Chemotherapy or best supportive care
Previously treated stage IV
Check point inhibitor Combination or monotherapy
BRAF-MEK inhibitor
What is the prognosis of melanoma?
Patients with localised disease, and tumours <1mm deep have a >95% survival rate at 5 years.
Relapse occurs in a significant proportion of people with stage IIA to IIC melanoma (up to 50% at 5 years in people with stage IIC melanoma)
<30% diagnosed with distant metastasized melanoma survive over 5 years
What guidelines are used in melanoma?
ESMO
NICE
NCCN
What are the considerations when deciding whther a melanoma patient should start on immunotherapy or targeted therapy?
Start with immunotherapy
Long-lasting effect, and still have targeted therapy in the bag if/when needed
But relatively high rate of side effects, and significant rate of non-response
But fairly slow onset
Start with targeted therapy
Rapid effect (days/weeks)
Generally higher response rate
Lower rate of side effects
But relatively short duration of response
What is the incidence of CNS tumours?
Glioblastoma: annual incidence is approximately 3 per 100,000 per year and increases with age and male sex.
What are the risk factors associated with CNS tumours?
Age
Obesity
Exposure to vinyl chloride – glioma
EBV infection – implicated in primary CNS lymphoma
Transplant recipients and patients with AIDS – increased risk of primary CNS lymphoma
Ionising radiation
Radiofrequency radiation
Occupational exposures e.g. Meningiomas may be associated with lead exposure.
Family syndromes: NF1, NF2, VHL, LFS
How do patients with CNS tumours present?
Headaches
Seizures
Visual changes
GI symptoms e.g. loss of appetite, nausea, vomiting
Personality, mood, mental capacity, concentration changes
How are CNS tumours diagnosed?
Imaging
MRI: used as standard as has good tissue resolution. CT scan used when MRI is contradictory
PET: used to determine tumour from necrotic regions (metabolically active)
Histology
Biopsy- morphology, staining, IHC to determine grade/stage
Molecular
IDH1, MGMT, ATRX, 1p/19q codeletion, histone mutations
All involved in determining the subtype
What poor prognostic factors are associated with CNS tumours?
Age >40 years
Progressive disease
Tumour size >5cm
Tumour crossing midline
Contrast enhancement on MRI
WHO performance status (>1)
Neurological symptoms
Less than gross total resection
How have the WHO 2021 CNS classification guidelines changed from the 2016 guidelines?
The 2021 WHO classification emphasizes molecular diagnostics alongside traditional histopathology- integrated diagnosis.
Gliomas have also been distinguished into adult and paediatric
Introduced grading within tumour types
How are CNS tumours classified?
Adult-type diffuse gliomas
Pediatric-type diffuse low-grade gliomas
Pediatric-type diffuse high-grade gliomas
Circumscribed astrocytic gliomas
Glioneuronal and neuronal tumors
Ependymal tumors
Embryonal tumors
Meningioma
What are the major classifications of adult gliomas according to WHO 2021?
- Diffuse Astrocytic and Oligodendroglial Tumors
IDH-mutant gliomas
- Astrocytoma, IDH-mutant (graded 2, 3, or 4)
- Oligodendroglioma, IDH-mutant and 1p/19q-codeleted (graded 2 or 3)
IDH-wildtype gliomas
- Glioblastoma, IDH-wildtype (automatically grade 4)
- Diffuse midline glioma, H3 K27-altered (grade 4)
- Diffuse hemispheric glioma, H3 G34-mutant (grade 4) - Circumscribed Astrocytic Gliomas (Non-diffuse)
- Pilocytic astrocytoma (grade 1)
- Pleomorphic xanthoastrocytoma (grade 2)
- Subependymal giant cell astrocytoma (grade 1)
What molecular markers are used to classify adult gliomas according to WHO 2021?
Learn diagram
IDH (Isocitrate Dehydrogenase) Status
IDH-mutant: Associated with a better prognosis.
IDH-wildtype: Often associated with a poorer prognosis
1p/19q Codeletion
Presence of this codeletion is characteristic of oligodendrogliomas.
Histone Mutations
Mutations in histone genes such as H3 K27M (common in diffuse midline gliomas) and H3 G34R/V.
ATRX: rules out oligodendroglioma
How are CNS tumours graded according to WHO 2021?
Grade 1: Typically benign, slow-growing, and well-circumscribed tumors (e.g., Pilocytic astrocytoma).
Grade 2: Low-grade, but infiltrative and have potential for malignant transformation.
Grade 3: Anaplastic, more aggressive than grade 2.
Grade 4: Highly malignant and aggressive, such as glioblastomas and certain diffuse midline gliomas
What TD targets are there for gliomas?
SNVs: IDH1, IDH2, ATRX, H3-3A,H3C2, BRAF, TERT promoter
Structural: NTRK, EGFR vIII, BRAF
Methylation: MGMT
What are the common mutations and the clinical significance of IDH1/2 in gliomas?
IDH1 R132 and IDH2 R172
First stage of WHO classification (astrocytomas and oligodendrogliomas)
Better prognosis compared to IDH-wildtype gliomas.
Associated with a more favorable response to treatment, including radiotherapy and chemotherapy
What is the role of IDH enzymes and how do mutant IDH drive CNS tumours?
Isocitrate dehydrogenase (IDH) enzymes, of which there are three isoforms, are essential enzymes that participate in several major metabolic processes, such as the Krebs cycle, glutamine metabolism, lipogenesis and redox regulation.
Mutations usually in the isocitrate binding site, reducing isocitrate binding and altering cellular metabolism
How is IDH mutant detected in CNS?
IHC
- R132H-specific Ab
- 85-90% R132H but can’t detect other variants
NGS
- Panel genes, full gene sequencing
Targeted hosptot
What is the clinical significance of 1p/19q codeletion in gliomas?
Characteristic of oligodendrogliomas.
Associated with a better prognosis and response to therapy.
Key criterion for differentiating between oligodendrogliomas and astrocytomas.
How is 1p/19q codeletion detected in gliomas?
ATRX IHC: Surrogate marker based upon mutual-exclusivity with 1p19q co-deletion. Rapid, relatively cheap, and labour unintensive.
FISH: Reliable and cost effective. FISH cannot differentiate between whole chr. Arm deletion from smaller focal deletions.
SNP arrays: can identify whole-arm co-deletion with higher reliability – better choice but labour intensity
PCR based microsatellite analysis: can allow detection of LOH at selected loci and NGS-based methods also useful
What is the clinical significance of ATRX in gliomas?
Commonly found in IDH-mutant astrocytomas, rules out oligodendroglioma.
ATRX mutation is mutually exclusive with 1p19q co-del
What is the clinical significance of TP53 in gliomas?
Frequently found in IDH-mutant astrocytomas
Can be detected by IHC or NGS
What is the clinical significance of MGMT in gliomas?
Promoter methylation
Predicts response to alkylating agent chemotherapy (e.g., temozolomide) in glioblastomas- associated with longer survival
What is the role of MGMT?
Removes alkyl groups and repairs mutagenic DNA lesions, preventing DNA damage and subsequent apoptosis. Therefore key in maintaining DNA integrity, but can provide a survival / cell death resistance mechanism by preventing cancer cells from entering the apoptotic pathway when subject to chemo-radio therapy.
How is MGMT promoter hypermethylation detected in gliomas?
Bisulfite conversion: Convert unmethylated cytosine residues to uracil, using bisulphitation of DNA (methylated cytosine is resistant to this chemical alteration)
Pyrosequencing
MLPA
Methylation specific PCR
What is the clinical significance of TERT in gliomas?
Almost all IDH-mutant, 1p/19q-codeleted oligodendroglial tumours have activating mutations in TERT gene promoter region – valuable diagnostic marker.
Associated with a poor prognosis.
TERT promoter mutations, along with EGFR amplification and +7/-10 copy number changes, are indicative of glioblastoma, IDH-wildtype.
What are the common TERT mutations seen in glioma and what do they do?
c.-124C>T, c.-146C>T
Produces a binding site for ETS transcription factors- gains the ability to recruit transcription factors that might upregulate TERT protein expression.
Leads to telomere maintenance in tumour cells
Detected by NGS
What is the clinical significance of histone H3 mutations in gliomas?
H3 K27M: Found in diffuse midline gliomas, particularly in the brainstem, thalamus, and spinal cord; associated with a very poor prognosis (2 year surival <10%) and classified as WHO grade 4, paediatric
H3 G34R/V: Found in diffuse hemispheric gliomas, typically in children and young adults; also associated with a poor prognosis.
What is the clinical significance of BRAF mutations in gliomas?
Common in pediatric low-grade gliomas
V600E in ganglioglioma
KIAA1594-BRAF fusion present in 70% pilocytic astrocytoma- aids diagnosis
Can be targeted by specific inhibitors (e.g., vemurafenib) in cases of refractory or recurrent tumors.
How are BRAF mutated gliomas treated?
V600E
- BRAF/MEKi FDA approved but not yet NICE approved
- Could access compassionally
KIAA1549:BRAF
- MEK inhibitor trial
What is the clinical significance of CDK2NA/B mutations in gliomas?
Indicative of a more aggressive tumor and associated with poor prognosis in IDH-mutant astrocytomas.
Important for grading and determining the aggressiveness of the tumor.
What is the clinical significance of EGFR mutations in gliomas?
Most frequently amplified in glioblastoma (30-40%), often associated with structural abnormalities e.g. mutant protein EGFRvIII – exon 2-7 skipping, characterised by deletion of extracellular domain (seen in ½ of all with amplification).
Most useful in diffuse gliomas lacking IDH mutations which fail to show high grade features (necrosis, MVP), a confounding presentation; EGFR amp confirms GBM, IDH-WT, WHO IV.
Poor prognosis
Potential therapeutic target
How are paediatric gliomas classified according to the WHO?
Pediatric-type diffuse low-grade gliomas
- Diffuse astrocytoma, MYB- or MYBL1-altered
- Angiocentric glioma
- Polymorphous low-grade neuroepithelial tumor of the young
- Diffuse low-grade glioma, MAPK pathway-altered
Pediatric-type diffuse high-grade gliomas
- Diffuse midline glioma, H3 K27-altered
- Diffuse hemispheric glioma, H3 G34-mutant
- Diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype
- Infant-type hemispheric glioma
What are embryonal tumours?
Replaces Peripheral neuroectodermal tumour (PNET)
Predominantly occur in children
Histologically characterised by high cellularity with densely packed, poorly differentiated small cells and marked mitotic activity.
What are the types of CNS embryonal tumours?
Includes:
Medulloblastomas
Embryonal tumours with multi-layered rosettes (ETMRs)
Atypical teratoid/rhabdoid tumours (AT/RTs)
+ heterogenous group of other embryonal CNS tumours
How are medulloblastomas classified?
WNT activated
SHH activated/TP53 WT
SHH activated/TP53 mutant
Non-WNT
