Colorectal Flashcards
(73 cards)
What are the boundaries of the rectum
From dentate line (margin with anal canal) to rectosigmoid junction
What is the nodal drainage of the rectum
2/3 to para-rectal LNs -> inferior mesenteric nodes
1/3 to internal iliac nodes
What are the MMR proteins
MLH1
PMS2
MSH2
MSH6
What rate of MMR deficiency is sporadic
2/3
1/3 germline
Loss of which proteins indicates potential Lynch syndrome
MSH2 and/or MSH6 loss - paired - suspect Lynch syndrome
MLH1 & PMS2 loss - paired - need to determine B-Raf mutation or B-raf promotor hypermethylation
Approximately 1/3 have B-RAF mutation
B-RAF mutated: Unlikely to be Lynch (more likely MLH1 somatic acquired mutation)
B-RAF wild-type & no promoter hypermethylation - likely Lynch
What is Lynch syndrome
What is the inheritance
What is the lifetime risk of colorectal cancer
germline AD loss of MMR function, causing microsatellite instability
80% lifetime risk, typically right-sided tumours
What is Muir-Torre syndrome
What cancers are predisposed
What genes are affected
Subtype of Lynch syndrome
Develop colon, GU, and skin lesions - keratoacanthomas and sebaceous tumours
Genes affected = MLH1, MSH2, and MSH6
What tumours are associated with Lynch syndrome
What screening takes place
Renal
Upper GI - pancreatic and gastric
Ovarian and endometrial
2yrly colonoscopy from age 25
2yrly OGD from age 50-70
Consider TAH+BSO from age 40
What are the criteria within the Modified Amsterdam Criteria, to suggest Lynch syndrome
3+ relatives affected, with a related cancer (colorectal, small bowel, gastric, pancreatic, endometrial, ovarian, renal pelvis TCC (but not bladder))
2 generations affected
1 person diagnosed <50yrs
1 must be a first degree relative
Must exclude FAP
How is FAP inherited
What is the gene and chromosome
What surveillance takes place
AD inherited loss of APC on chromosome 5
Colonoscopy from age 15
What are the variants of FAP (3)
Gardner’s syndrome - colorectal polyps, skull and mandible osteomas, desmoid tumours & cysts, sebaceous cysts
Turcot’s syndrome - Colorectal polyps with CNS tumours (ependymomas, medulloblastomas)
Attenuated FAP - fewer polyps and lower risk of cancer
What is Gardner’s syndrome & what are its features
Variant of FAP
colorectal polyps, skull and mandible osteomas, desmoid tumours & cysts, sebaceous cysts
What is Turcot’s syndrome & what are its features
Variant of FAP
Colorectal polyps with CNS tumours (ependymomas, medulloblastomas)
What breast variant can metastasise to the bowel
Lobular breast cancer
What does B-raf predispose to
R sided tumours, worse prognosis
What are the commonest Ras mutations seen in colorectal cancer
What are the treatment implications
Ras G12 mutations
Can only given EGFR inhibitors (cetuximab / panitumumab) in Ras WT tumours
What screening exists for colorectal cancer
What is the outcome
Faecal immunohistochemical test (FIT)
Age 60-74 - 2-yearly
If ≥75 – can request to keep testing
Approx. 2% are positive -> undergo colonoscopy of which 1/300 will have cancer
High false positive rate (>90%)
Approx.15% reduction in mortality from screening (Nottingham trial 2006)
What investigations are needed for a newly diagnosed bowel cancer
Histology incl B-Raf & Ras status, and MMR
Imaging - CTCAP, MRI pelvis for rectal cancer
What are the Duke’s staging for colorectal cancer
A - T1-2 N0
B - T3-4 N0
C - T Any N1-2
D - metastatic disease
When should a colonoscopy be repeated following removal of an adenoma
1-2yrs
When should a colonoscopy be repeated following removal of an adenocarcinoma of pT1 only (submucosal invasion, not muscular)
1-2yrs
What risk factors would make a pT1 adenocarcinoma seen on colonoscopy, better managed by surgical workup and removal rather than removal at colonoscopy
Lymphatic or venous invasion
Grade 3 differentiation
Significant tumour budding
How is a stage 1 (T1-2 N0) colorectal cancer managed
Surgery only - no benefit to adjuvant chemotherapy
What are the options for neoadjuvant chemotherapy
and what duration
CapOx - capecitabine and oxaliplatin (3wkly regimen)
FolFox - Folinic acid, 5-FU, oxaliplatin (2wkly regimen)
6wks - 2 cycles capox or 3 cycles folfox