Colorectal Cancer Flashcards
-Pathology -Patterns of spread -Staging -Management
What is the epidemiology of colorectal cancer?
- Approx 41,000 new cases yearly in UK
- 4th most common malignancy after lung cancer
- 10-15% of all malignancies
- Causes 16,000 deaths
- cancer of colon 1.5 times more likely thant rectal cancer
What are the risk factors for colorectal cancer?
- Diet
- rich in animal fats and meat
- poor in fibre
- common in western countries
- Inflammatory bowl disease -associated with Ulcerative Colitis but not Crohns
- Familial association
- hereditary non-poluposis colon cancer (HNPCC): mutations in HNPCC repair genes
- familial adenomatous polyposis (FAP): mutation in APC gene
- Gardner’s syndrome
What is the histology of colorectal cancer? What areas is it commonly found in?
Area affected
- 40% of large bowel cancers occur in rectum
- 20% in the sigmoid colon
- 6% in the caecum
- Rest in the remaining colon
Histological Sub-type
- Epithelial: 90-95% adenocarcinoma
- Carcinoid
- Gastrointestinal stromal tumour
- Primary malignant lymphoma
How can colorectal cancer spread?
- Local invasion
- Lymphatic
- Venous
- Trans-coelomic spread within the peritoneal cavity
What is the presentation of colorectal cancer?
- Altered bowel habit
- weight loss
- rectal bleeding
- vague abdominal pain
- occult tumours on the right side =can present with iron deficiency anaemia
What initial investigations should be done if colorectal cancer is suspected?
- Rectal examination
- 3/4 of rectal lesions can be felt by digital examination
- Rigid/flexible sigmoidoscopy and colonoscopy
- visualisation and allows biopsy of suspicious lesions
- CT
- provides stagins
- Double contrast barium enema =less useful
- Tumour marker CEA (carcino-embryonic antigen)
- not diagnostic
- used to monitor disease
What two staging systems are used in colorectal cancer?
- TNM system
- Dukes Stage
Explain what these mean in staging colorectal cancer:
- TX
- T0
- T1
- T2
- T3
- T4
- N0
- N1
- N2
- MX
- M0
- M1
- M1a
- M1b
- M1c
- TX: primary tumour cannot be assess
- T0: No evidence of primary tumour
- T1: tumour invades submucosa
- T2: tumour invades muscularis propria
- T3: tumour extends through muscularis propria into peri-colic tissues
- T4: tumour invades visceral peritoneum or invades / adheres to adjacent organ or structures
- N0: no regional lymph node involvement
- N1: involvement of 1-3 lymph nodes
- N2: Involvement of 4 or more lymoh nodes
- MX: Distant metastasis cannot be assess
- M0: no distant metastasis
- M1: distant metastasis
- M1a: confined to one organ or site (e.g. liver or lung) but not peritoneum
- M1b: 2 or more site (but not peritoneum)
- M1c: peritoneal spread
What does each of these mean in the staging of colorectal cancer, using Dukes Stage:
- A
- B
- C
- D
- A = invasion into but not through the bowel wall
- B = invasion through the bowel wall but not into nodes
- C = lymph node involement
- D = distant metastases
What are the option of management of colorectal cancer?
- Surgery
- radical resection =standard treatment for primary colorectal carcinoma
- patients with early stage are usually cured by surgical resection alone
- surgery still indicated in patients with advanced disease
- resection of liver metastases in addition to primary may be beneficial
- Radiotherapy
- predominantly used in treatment of rectal carcinoma
- not commonly used in colon cancers because of potential toxicity to adjacent organs and mobility of the tumours
- Chemotherapy
- adjuvant chemotherapy for high risk colorectal cancer
- in Dukes C cancer, 6 months of adjuvant treatment may increase long term survival from 40-60%
- Not clear role for Dukes B cancer
- 5-FU is the most active agent in colorectal carcinoma
- Newer drugs such as oxaliplatin and ironotecan now also in use
What is the prognosis of colorectal cancer?
Duke stage and 5-year survival
Stage 1: 80%
Stage B: 50%
Stage C: 15-40%
Stage D: 5%
Age below 40 is adverse prognostic factor possibly reflecting a biologically more aggressive tumour
