oncology Flashcards
what are oncogenes?
needed for normal growth and are tightly controlled but the control can be lose with mutation
can be expressed by some viruses
what are tumour supressor genes?
stop cells from proliferating out of control
how are tumour supressor genes function lost?
by both copies being mutated / deleted / silenced
how many mutations need to be acuumulated to initiate a tumour?
10-12
what are the 6 hallmarks of cancer?
1) sustaining proliferative signalling
2) evading growth suppressors
3) resisting cell death
4) enabling replicative immortality
5) inducing angiogenesis
6) activating invasion and metastasis
why is sustaining proliferative signalling useful? and how does it happen?
can become self sufficient at growth
- endogenous growth factors
- mutated growth factor receptors so always turned on
- over express growth factors so respond to tiny amounts
- mutate intracellular pathway so always activated
what is the therapy target for sustaining proliferative signalling?
EGFR inhibitors
how do they evade growth suppressors?
resist tumour suppressor genes -
- Rb controls cell cycle progression
- p53 halts cycle if not normal
what is the therapy target for evading growth supressors?
cyclin dependant kinase inhibitors
how do cells resist cell death?
-avoid caspase cascade
- extrinsic pathway via death receptors
- intrinsic pathway from DNA damage
- resistance to anti-cancer drugs
what is the therapy target for resisting cell death?
Pro-apoptic BH3 mimetics
how do cells enable replicative immortality?
telomerase adds telomeres on
what is the therapy target for replicative immortality?
telomerase inhibitor
how does a tumour induce angiogenesis?
secretes vascular endothelial growth factor (VEGF)
what is the therapy target for angiogenesis?
VEGF inhibitor
what is the therapy target for invasion and mets?
HGF / c-met inhibitor
What are the 4 emerging hallmarks?
1) deregulating cellular energetics / reprogramming energy metabolism
2) evading immune destruction
3) genome instability and mutation
4) tumour promoting inflammation
What is the therapy target for deregulating cellular energetics?
aerobic glycolysis inhibitors
what is the therapy target for evading immune destruction?
immune activating anti-CTLA4 mAb
what is the therapy target for genome instability?
PARP inhibitors
what is the therapy target for tumour promoting inflammation?
anti-infl drugs
how may inflammation promote tumours?
provides growth factors, cytokines and immuno suppression
what are the characteristics of a feline injection site sarcoma?
- previous FeLV or rabies vax
- at site of inj
- non painful
- firm
- fixed
- locally invasive
- cystic
- fast growing
How do you diagnose a feline injection site sarcoma?
incisional biopsy
what is the 321 rule with feline injection site sarcomas?
its likely to be one if its over 3 months since a vax, over 2 cm and has increased in size 1 month post vax
why is cytology not useful at diagnosing feline infection site sarcomas?
- as cystic so may just take cystic fluid so not representative
- cant grade it
- if under a month since vax then inflammation may still become neoplastic
why would you not do an excisional biopsy to diagnose feline injection site sarcoma?
- no long term benefit
- can affect prognosis as with second curative surgery may have mets, inflammation and fibrosis, seeding through tissue planes and will need larger margins, altered anatomy, less tissue to close with
how do you treat feline injection site sarcomas?
- radical 1st surgery with 3-5 cm margins
- adjuvant radiation for 3-4 w
how can you avoid feline injection site sarcoma?
dont over vacc
dont repeatedly vaccinate in the same location
put vax in distal rear limb
use adjuvant free vax
what can cytology tell you / not tell you?
tell you - cell type, morphology
not - architecture, mitotic index, invasion, vasculature / lymph
What can histopathology tell you?
cell type morphology tissue architecture mitotic index vasculature / lymph necrosis
what are the 3 main categories ?
epithelial
mesenchymal
round cell
what is an epithelial tumour called?
carcinoma
what is a mesenchymal tumour called?
sarcoma
what information is used to grade a tumour?
mitotic index cellular differenatiation invasion of surrounding tissues vascular / lymph necrosis
how is a tumour stages?
TNM
- T = primary tumour size (T1-3)
- N = regional LN (N0 = no mets , N1 = mets)
- M = distant mets (M0=none , M1=some)
what is paraneoplastic syndrome?
systemic effects of a tumour, occuring at sites distant to the tumour due to hormones, cytokines or enzymes from the tumour
what can high calcium cause?
PU/PD anorexia depression weakness bradycardia
What can low glucose cause?
weak
collapse
seizures
What can viscose bloody cause?
neuro signs
retinal detachement
What is neoplasia?
a monoclonal, uncontrolled proliferation of cells that continues in the absence of the inciting cause
what is seen grossly with a benign tumour?
grow by expansion slow growth well demarcated smooth outline CT capsule freely mobile homogenous cut surface little haemorrhage or necrosis surgical removal easy no recurrence if fully excised no metastasis
what is seen grossly with a malignant tumour?
grow by invasion ulcerative on surface not encapsulated not mobile on palpation necrosis and haemorrhage removal difficult often recurs mets
what is seen micrscopically with benign tumours?
similar to tissue of origin well organised can be functioning doesnt breach capsule few / no mitotic cells
what is seen microscopically with maliganant tumours?
loss of cohesiveness and structure no capsule increased mitotic index variable cell size +shape = pleomorphism variable nuclei size +shape = anisokaryosis increased nucleus : cytoplasm ratio prominent nuclei multinucleated syncytia necrosis fibrosis inflammtion
what is a benign surface and gut ep tumour?
papilloma
benign glandular ep?
adenoma
malignant surface and gut ep
carcinoma
malignant glandular ep
adenocarcinoma
fibrous benign
fibroma
bone benign
osteoma
cartilage benign
chondroma
adipose benign
lipoma
smooth muscle bening
leiomyoma
endothelium benign
haemangioma
skeletal muscle benign
rhabdomyoma
fibrous malignant
fibrosarcoma
bone malignant
osteosarcoma
cartilage malignant
chondrosarcoma
adipose malignant
liposarcoma
smooth muscle malignant
leiomyosarcoma
endothelium malignant
haemangiosarcoma
skeletal muscle malignant
rhabdomyosarcoma
what is a granuloma?
chronic inflammation
what is a lymphoma?
malignant tumour of lymphoid system
what is a melanoma
benign or malignant melanocyte tumour
what is leukaemia?
tumour from bone marrow cells and circulates in blood
what is a teratoma?
germ cell tumour with eco/endo/meso derm
what is a sarcoid?
equine skin low grade fibrosarcoma
how do carcinomas metastasise?
in the lymphatics
draining LN has some deposits
how do sarcomas metastasise?
in blood
seeds to other organs
how do mesotheliomas spread?
across serosal surfaces
what does a high grade mean?
poorly differentiated
worse prognosis
what does a low grade mean?
well differentiated
better prognosis
what is chemotherapy?
cytotoxic drugs used in cancer treatment that interfere with cell growth / division of rapidly dividing cells
what are the indications for chemotherapy?
- primary treatment for disseminated disease
- adjuvant therapy after surgery for highly metastatic tumours
- after incomplete resection
- neo-adjuvant to shrink before surgery
- treatment of inoperable tumours
- primary treatment for transmissible venereal tumour
how does chemotherapy work?
affects different stages of the cell cycle
works best on actively dividing cells with a high mitotic index
when is it best to use chemotherapy?
early on in disease when the cells are still dividing
what is the cell kill hypothesis?
cell killing follows a first order kinetics so a given dose will kill a fixed percentage of the tumour population
why do we pulse dose chemotherapy?
to allow times in between for normal tissue to recover but not enough time for tumour to regrow
why do we use combination chemotherapy?
to avoid resistance
drugs to act on different parts of the cell cycle
what are the 4 stages of chemotherapy?
1) induce
2) maintenance
3) re-introduction
4) resuce
what are 2 alternative chemotherapies?
- metronomic / continuous low dose chemo
- receptor tyrosine kinase inhibitors
what is metronomic / continuous low dose chemo?
- almost continual low dose given with a NSAID
- aim is to slow growth by inhibiting angiogenesis
- tumours may not shrink but disease should become stable
what are 4 factors affecting chemo success?
- tumour type
- penetration of drug into tumour
- development of drug resistance
- multi drug resistance
what are 4 common adverse effects of chemo?
- myelosuppression
- GI toxicity
- poor hair growth
- drug extravasation(outside vein)
when will neutrophils and platelets be at their lowest after chemo?
neutrophils - 7d
platelets - 10 d
what do you do if chemo has induced vomiting?
bland diet
gut protectant
anti-emetics
what do you do if chemo has induced diarrhoea?
bland diet
metronidazole
what do you do if the drug is know to affect the chemoreceptor trigger zone (CTZ)?
give phrophylactic anti-emetics
How do alkylating agents work?
- not cell cycle specific
- replaces alykyl group with H+ in DNA causing cross linkage and DNA breakage
- interferes with replicaiton / transcription
what are some examples of alkylating agents?
cyclophosphamide lomustine melphalan chlorambucil procarbazine dacarbazine
what is cyclophosphamides specific toxicity?
haemorrhagic cystitis in dogs
give plenty of water and chance to urinate
what is lomustines toxicity?
hepatotoxicity in dogs (monitor ALT)
nephrotoxicity
what do mitotic spindle inhibitors do?
cell cycle specific
binds to tubulin so prevents normal microtubule assembly
what are some examples of mitotic spindle inhibitors?
vincristine
vinblastine
vinorelbine
taxanes
what is vincristines toxicity?
peripheral neuropathies
cat constipation
how do anti-metabolites work?
cell cycle specific
mimic normal substrates needed for nucleic acid metabolism so interfere with DNA synthesis
what are some examples of anti-metabolites?
cytosine methotrexate hydrocarbameide 5-fluoruracil gemcitabine azathiopine
what is 5-FU toxicity?
cat nephrotoxicity
what do anti-tumour antibiotics do?
prevent DNA and RNA synthesis
what are some examples of anti tumour antibiotics?
doxorubicin
epirubicin
mitoxantrone
actinomycin
what is doxorubicins toxicity?
cardiotoxicity in dogs
mast cell degranulation
nephrotoxic
what do platinum compounds do?
cell cycle non specific
cause inter and intra strand crosslinks so affects synthesis and transcription
what are some examples of platinum compounds?
cisplastin
carboplatin
what is the toxicity of platinum compounds?
pulmonary oedema
nephrotoxic
vomiting
what would you give corticosteroids to help neoplasia?
apoptosis of lymphoid and mast cells
what would you give L-asparginase to neoplasia?
neoplastic lymphoid cells rely on L-aspargine
what would you give NSAIDs to neoplasia?
inhibit angiogenesis
promote apoptosis
anti infl
analgesia
why would you give receptor tyrosine kinase inhibitors?
interfere with cell signalling needed for cell growth, proliferation and survival
MCT esp
when is a biopsy indicated?
if treatment would be affected by tumour type
owners willingness affected by prognosis
guidelines for biopsy
- dont compromise further treatment
- dont breach fresh anatomic planes
- use fresh instruments for each site
- include normal and abnormal tissue
- try not to deform specimen by forcceps
- tissue should be <1cm thick in 10%formalin
what is prophylactic surgery?
removal of a tissue which will reduce tumour incidence
e.g gonadectomy or suspected pre-cancerous lesion
what are the advantages and disadvantages of curative surgery?
+ = immediate cure, not carinogenic, no local toxicity, not immunosupressive, remove large mass
- = local cure only, change in cosmeis, change in function
what are the principles of curative surgery?
- plan surgery and reconstruction
- do as early as possible
- first surgery has best chance
- good margins in all 3 dimension
- dont compromise margins for cosmesis
8 practical considerations for curative surgery
1) cosmesis and function
2) pre-op preparation (dont scrub too hard as disseminate, Abx?)
3) dissection technique (atraumatic)
4) reduction of contamination (dont handle tumour, change to clean gloves etc for closure)
5) avoid wound complications (be gentle)
6) vascular occlusion (prevent diseemination)
7) LN removal for staging
8) reconstruct defecit
what is a local excision? and indications?
tumour removed through its natural capsule with minimum adjacent tissue
benign tumour with no tendency to infiltrate
what is a wide local excision? and indications?
tumour removed with appropriate margins, dont enter clean fascial planes
benign infiltrating, malignant non infiltrating
what is radical local excision and indications?
tumour removed on all aspects with a clean fascial plane - compartmental, muscle group, amputation
tumours with a pseudocapsule
what is cytoreductive surgery?
planned incomplete removal to improve efficacy of other treatment or retain essential anatomy or tumour highly likely to recur
what is pallative surgery?
improve quality but not always length of life
pain relief
what are the indications for radiation?
incompleteley resected tumour
shink non resectable tumours
pain control (destroys recceptors)
how does radiation work?
induces direct and indirect DNA damage
want damage bad enough to cause cell death, or alive but cant divide
Why do we fractionate radiations? (4Rs)
spares normal tissue because it allows repair of sublethal damage and repopulation
increases damage to the tumour because of reoxygenation and redistribution of cells into radiosensitive phases of cells cycle
what is reoxygenation in regards to radiation?
only the vascularised cells on the tumour periphery are affected by radiation so the necrotic core has more room so outside becomes perfused so can then destroy that.
therefore we fractionate
what is a curative dose of radiation?
2-3 Gy / d for 3 w
8 neoplasms that can be cured with radiation? (maybe with surgery combined)
nasal tumours brain tumours oral tumours sq cell tumours epulis soft tissue sarcoma feline injection site sarcoma oral fibrosarcoma
what is an epulis?
benign tumours of gingiva / alveolar
what is a pallative radiation dose?
6-7 Gy/week for 4w
3 reasons that radiation can be used pallatively for
radiosensitive tumours with high mets rate
shrinking mass effect
pain control (esp in bone)
what are the acute side effects of radiation?
- skin - erythema, dermatitis, alopecia (collar and analgesia)
- MM - hypersalivation, discharge, mucositis (analgesia, feeding tube)
- eyes - conjuctivitis, blepharitis, cornea ulceration (optimmune treatment)
- CNS - edema, transient demyelination (corticosteroids)
what do acute radiation effects appear and go?
see them 7-10 d post treatment
self limiting and resolve in a few weeks
what are the late side effects of radiation?
- Skin - fibrosis, alopecia, pigment changes
- eyes - cataracts, chronic keratoconjunctivitis sicca
- CNS - necrosis of white matter, vasculopathy
What are the late side effects of radiation seen?
after 6 months