colorectal ca Flashcards
definition of colorectal ca
Malignant adenocarcinoma of the large bowel.
Rf of colorectal Ca
- neoplastic polyps
- IBD - especially longstanding UC
- genetic predisposition <8% eg FAP and HNPCC
- diet - low fibre, high red and processed meat, fat, sugar, reduced veg and fibre intake
- high alcohol
- smoking
- previous cancer
- FH
aetiology of colorectal ca
A sequence from epithelial dysplasia leading to adenoma and then carcinoma is thought to occur, involving accumulation of genetic changes in oncogenes (e.g. APC, K-ras) and tumour suppressor genes (e.g. p53, DCC).
prevention of colorectal ca
prevention - aspirin >=75mg/d reduces incidence and mortality
pathology of colorectal ca
- 60% rectum ad sigmoid
- 30% asc colon
- rest in descending and transverse
- distal = annular encircling ring around the bowel wall = apple core constrictions
- prox = polyploid, exophytic masses
- neoplastic change with deranged adenomatous or anaplastic cells and varying degrees of bowel penetration
- staging: Duke’s and TNM
spread of colorectal ca
local, lymphatic and by blood (liver, lung and bone) or transcoelomic
epidemiology of colorectal ca
3rd most common cancer
2nd most common cause of UK cancer deaths - 16000/yr
usually adenocarcinoma
86% of presentations are in >60yrs old
Sixty percent occur in the rectum and sigmoid colon; 15–20% in the ascending colon;
rectal male>female, colon female>male
sx of rectal ca
weight loss
constipation
bloating
blood mixed in stool
tenesmus - dont feel like emptied bowel properly
sx of L sided colorectal ca
bleeding/mucus PR
altered bowel habit or obstruction 25% - colonic diameter smaller and bowel content more solid
tenesmus (sensation of incomplete emptying after defecation)
mass PR (60%)
sx of R sided colorectal ca
later presentation
reduced weight
reduced Hb - IDA, blood loss from ulcerated surface
abdominal pain
obstruction less likely
non-specific malaise
general sx of colorectal ca
abdominal mass
perforation
haemorrhage
fistula
Up to 20% of tumours will present as an emergency with pain and distension caused by large bowel obstruction, haemorrhage or peritonitis as a result of perforation.
signs of colorectal ca
palpate mass in rectum on DRE
anaemia may be the only sign - particularly in R sided
abdo mass
hepatomegaly if met
shifting dullness of ascites
ix of rectal c
colonoscopy to patients w/o major comorbidity to confirm diagnosis of colorectal cancer
or sigmoidoscopy
If lesion suspicious of cancer is found – biopsy to get histological proof
ix of colorectal ca
FBC - microcytic anaemia
faecal occult blood, or frank blood in stool
tumour markers (CEA to monitor treatment response or disease recurrence)
sigmoidoscopy or colonoscopy - can be done ‘virtually’ by CT - allows visualisation and biopsy
polypectomy can also be performed if isolated small carcinoma in situ
LFT
liver MRI/US
CEA may be used to monitor disease and effectiveness of treatment
if FH or FAP = refer for DNA test once >15yrs
barium contrast studies - apple core stricture on barium enema
abdo US for hepatic met
CXR, CT or MRI and endorectal US can be used for staging
mx of colon cancer
surgery
if obstruction - stent or resect
chemotherapy - 5FU and oxaliplatin
