Colorectal Cancer Flashcards
The majority of colorectal cancers are what?
Adenocarcinoma (95%)
What are the risk factors for sporadic colorectal cancer?
Advanced age
Male
Previous adenoma/CRC
Environmental
What are the environmental risk factors for CRC?
Diet (low fibre, calc, high red meat) Alcohol Obesity Low exercise Smoking DM
What are colorectal adenomas?
Colorectal polyps, usually benign
Tubular or villous
What factors make colorectal adenomas high risk?
Size
Number
Degree of dysplasia
Villous architecture
What actions cause an adenoma to become a carcinoma?
Activation of oncogenes
Loss of tumour suppressor genes
Defective DNA repair pathway
What oncogenes are involved in adenocarcinoma formation?
k-ras
c-myc
What tumour suppressor genes are involved in adenocarcinoma formation?
APC
p53
DCC
How does colorectal cancer present?
Rectal bleeding Altered bowel habit Iron deficiency anaemia Palpable rectal/low right mass Acute colonic obstruction Systemic symptoms
What investigations would you give for a patient with suspected colorectal cancer?
Colonoscopy (therapeutic too)
CT abdo - barium enema
How is colorectal cancer staged?
CT scan
MRI
PET/EUS
When is MRI used for staging of a colorectal tumour?
Rectal tumours
What criteria is used for staging colorectal cancer?
TNM
Duke’s
What is Duke’s A criteria?
Confined to submucosa
What is Duke’s B criteria?
Invasion through muscularis without lymphatic involvement
What is Duke’s C criteria?
Invasion through muscularis with regional lymph node involvement
What is Duke’s D criteria?
Presence of distant metastases
How does the T staging work for colorectal cancer
T1 - confined to submucosa
T2 - Confined to muscularis
T3 - confined to serosa
T4 - breached serosa
How does the N staging work for colorectal cancer
N0 - no nodes involved
N1 - Up to 3 regional nodes
N2 - 4+ nodes
How are most colorectal cancers treated?
Surgery
When is colorectal cancer treated endoscopically?
Dukes A
Cancerous polyps
How is chemotherapy used for colorectal cancer?
Dukes C, B
Adjuvant therapy
Micrometastases
How is radiotherapy used for colorectal cancer?
Rectal cancer only
Neoadjuvant +/- chemo
What therapy is indicated for palliative care?
Chemotherapy
Stenting
How can the prognosis of colorectal cancer be improved?
Prevention (lifestyle)
Screening
What are the main forms of colorectal population screening?
Fecal occult blood test Faecal immunochemical test Flexible sigmoidoscopy Colonoscopy CT Colonography
Who are the high risk groups for colorectal cancer?
Heritable conditions
Inflammatory bowel disease
Familial risk
Previous CRC
What is FAP?
Familial adenomatous polyposis
What type of genetic condition is FAP?
Autosomal dominant
How does FAP affect the body?
50% adenomas in colon by 15yrs
95% by age 35yrs
What causes FAP?
Mutation of APC on chromosome 5
How are FAP patients treated?
Annual colonoscopy from age 10-12yrs (screening)
Prophylactic proctocolectomy
Extracolonic manifestations of FAP
Duodenal adenomas
CHRPE (retinal epithelium hypertrophy)
What is HNPCC?
Autosomal dominant mutation in DNA mismatch repair gene
Microsatellite instability
How are HNPCC patients screened?
2 yearly colonoscopy
What are HNPCC patients at risk of?
Early onset CRC (right sided)
Other, local cancers
How is HNPCC diagnosed?
Bethesda genetic testing
How are patients at high moderate risk due family history of CRC screened?
5 yearly colonoscopy from 50yrs
How are patients at low moderate risk due family history of CRC screened?
One colonoscopy at 55 years
How are IBD patients screened for colorectal cancer?
Colonoscopy 10 years post diagnosis
Dependent thereafter
How are previous CRC patients screened for colorectal cancer?
5 yearly colonoscopy
Which patients are considered high moderate risk of colorectal cancer?
CRC in 3 FDR, none <50
CRC in 2 FDR, mean age <60
Which patients are considered low moderate risk of colorectal cancer?
CRC in 2 FDR >60yrs
CRC in 1 FDR <50yrs
The majority of adenocarcinomas originate as what?
Adenomas - polyps
Adenomas can take which shapes?
Pedunculated
Sessile
What is the therapeutic benefit of colonoscopy?
You can find and remove any polyps
How do you prepare a patient for colonoscopy?
Sedation
Bowel prep - laxatives
When is CT colonography indicated in colorectal cancer?
When a patient is ineligible for colonoscopy
When is CT abdo/pelvis indicated in colorectal cancer?
When patient cannot undergo bowel prep - only shows very large cancers
What treatment is indicated for liver metastases?
Partial hepatectomy
Rectal tumour treatment always result with what?
Colostomy
Neoadjuvant radiotherapy
Which CRC patients get adjuvant chemotherapy?
Dukes C
- lymphatic spread
What lifestyle changes can reduce risk of CRC?
30m exercise a day
Maintain healthy BMI
Eat 5 a day
Smoking cessation
Who are screened for CRC, and how often?
50-74 year olds
FOBT every 2 years
Why was FOB replaced with FIT?
FOBT has lower sensitivity in women
FIT is a more simple test
Patients testing postive in FOBT are followed up how?
Colonoscopy
HNPCC is associated with what cancers?
CRC (right colon)
Endometrial
Genitourinary