Colorectal Cancer Flashcards
What is colorectal cancer?
Malignant adenocarcinoma of the large bowel
Describe the distribution of colorectal cancer
Distribution:
60%: rectum + sigmoid
30%: ascending colon
10%: rest of colon
Describe Dukes Classification of colorectal cancer, giving 5yr survival rates
A: limited to muscularis mucosae, 93%
B: extension through muscularis mucosae, 77%
C: involvement of regional lymph nodes, 48%
D: distant metastases, 6.6%
Describe the aetiology of colorectal cancer
Environmental + genetic
Sequence of genetic changes (e.g. APC then COX2 over-expression then K-Ras then p53) from epithelial dysplasia to adenoma to carcinoma, involving accumulation of genetic changes in oncogenes + TSGs.
Describe the epidemiology of colorectal cancer
2nd MOST COMMON cause of cancer death in the West
3rd most common cancer
UK: 20,000 deaths per year
Average age: 60-65 yrs
List 8 risk factors for colorectal cancer
Western diet (e.g. red meat, alcohol, low fibre) Obesity Colorectal polyps Previous colorectal cancer Family history IBD (UC > crohns) Alcohol Smoking
What do symptoms of colon cancer depend upon?
size + location of the tumour
List 3 signs of colorectal cancer
Anaemia, esp. in R-sided
Abdominal mass
Low-lying rectal tumours may be palpable on DRE
List 4 symptoms of left sided colon/ rectal cancer
Change in bowel habit
Rectal bleeding (blood or mucus mixed with the stools)
Tenesmus (due to space-occupying tumour in rectum)
Mass PR in 40-80% in rectal carcinomas
List 6 features/ symptoms of right sided colon cancer
Presents later Anaemia symptoms (lethargy) Weight loss Non-specific malaise Lower abdominal pain (rare) Abdo distention in advanced disease due to ascites or intestinal obstruction
What is tenesmus?
sensation of incomplete emptying after defecation
Name 2 genetic conditions associated with high rates of colorectal carcinoma
Familial adenomatous polyposis (FAP) Lynch Syndrome (HNPCC)
What bloods should be taken in colon cancer?
FBC: anaemia LFTs + renal function (baseline): usually norm even with liver mets Tumour markers (CEA): only measured on confirmation of dx
What stool based test is used in identifying colon cancer?
FOBT: screening test from 60-74yr every 2yrs ~10% of positive FOBT have bowel cancer detected at colonoscopy
What invasive investigations are performed for colorectal cancer?
Sigmoidoscopy
Colonoscopy: GOLD STANDARD: can biopsy tumour: confirms dx with characteristic pathological appearance
What investigations may be performed for visual inspection in colorectal cancer?
Double-Contrast Barium Enema: May show ‘apple core’ strictures
CT colonography (virtual colonoscopy)
Contrast CT TAP: For staging (Duke’s staging)
What tumour marker is associated with colorectal cancer? What is the main purpose of measuring this?
CEA
to detect relapse of cancer after surgical tx + evaluation of chemo
20% of colorectal tumours will present as an EMERGENCY with pain and distension. What is this due to?
Large bowel obstruction
Haemorrhage or peritonitis due to perforation
Give 2 signs that may be present when colorectal cancer has become metastatic
Hepatomegaly (lungs, liver + lymph N are likely)
Ascites
Cancers in which area would cause change in bowel habit with no rectal bleeding? What investigations should be performed in an over 60 year old with this presentation?
Ascending or transverse colon
Full colonoscopy
Why is obstruction and thus tenesmus more likely to occur in left sided colon/ rectal cancers?
Diameter is smaller on the left side + bowel content more solid.
