Colorectal Carcinoma

Question 1

Presentation

Answer 1

• ALARM SYMPTOMS not SPECIFIC/SENSITIVE to DETECTING COLORECTAL CANCER
  
  • PERSISTENT LOWER ABDOMINAL PAIN/BLOATING/DISCOMFORT - always caused by EATING + may be ASS. w/ LOSS of APPETITE or UNINTENTIONAL WGT. LOSS

Bleeding:
• PERSISTENT BLOOD MIXED W/ STOOL OR RECTAL BLEEDING (if bright = maybe anal cancer)

• IRON DEFICIENCY ANAEMIA (men any age, non-menstruating women) - MORE LIKELY TO BE R. SIDED
• MAY PRESENT W/ ACUTE GI BLEED = RARE

Persistent Bowel Changes:
• ALTERED BOWEL HABIT: LOOSE STOOLS > 4WKS

• PALPABLE RECTAL/R. LOWER MASS
• ACUTE COLONIC OBSTRUCTION IF STENOSING TUMOUR

Systemic Symptoms of Malignancy:
• WGT. LOSS
• ANOREXIA

Question 2

Investigations

Answer 2

Diagnosis - imaging = Colonscopy (+ tissue biopsies), Barium enema, CT colonography, CT abdo.pelvis

Staging = CT chest/abdo/pelvis, MRI (rectal lesions), PET scan, Rectal endoscopic USS - TNM, Duke’s staging (a = submucosa; b = muscularis mucosa + no nodes; c = muscularis + nodes; d = distant metastasis)

Question 3

Management

Answer 3

Radical = surgery (endoscopy/local excision), chemotherapy (adjuvant for duke’s c+), RT (rectal cancer)

Palliation = chemotherapy, colonic stenting

Question 4

Histology

Answer 4

primarily adenocarcinoma - 2/3 in colon + 1/3 in rectum

most arise from pre-existing polyps

genes = oncogene activation (k-ras, c-myc), tumour suppressor gene loss (APC, p53, DCC), defective DNA repair pathway genes (microsatellite instability)

Question 5

Risk factors

Answer 5

85% - sporadic - no genetic influence

ageing, male, previous adenoma/CRC, poor lifestyle (DM, smoking, poor diet, lack of exercise, obesity)

10% - familial risk - inheritable conditions e.g. HNPCC, FAP, other CRC syndrome

1% - underlying IBD

Question 6

Screening - Average Risk Group

Answer 6

FIT testing every 2 years - if +ve - colonoscopy

Question 7

Screening - HNPCC + FAP + IBD

Answer 7

HNPCC = autosomal dominant DNA mismatch repair gene mutation - early onset CRC + RHS, screening from 25yrs - colonoscopy every 2 years

FAP = autosomal dominant APC mutation, high risk of malignant change in early adulthood + multiple adenomas throughout colon - screening from 10-12yrs - annual colonoscopy + prophylactic proctocolectomy at 16-25yrs

IBD = index surveillance colonoscopy 10yrs after diagnosis - then dependant on duration, extent, inflammation activity, dysplasia presence

Question 8

Screening - Familial risk + Previous adenoma/CRC

Answer 8

Familial risk = high moderate risk (colonoscopy every 5yrs once 50yrs); low risk (once-only colonoscopy when 55yrs)

Previous CRC = coloscopy every 5yrs

Previous adenoma = depends of polyp no., size, dysplasia