Colon Cancer Clinical Overview

Written By Danial Mirza

Management of Colorectal Cancer: A Practical Guide for House Officers

I. The "On-Call" Snapshot

  • Clinical Significance in Malaysia: This is the most common cancer in Malaysian men and the second most common in women. You will encounter this frequently, often presenting late with complications like obstruction or perforation.

  • High-Yield Definition: Colorectal carcinoma (CRC) is a malignancy arising from the epithelial lining of the colon or rectum. Most are adenocarcinomas developing from adenomatous polyps. (Source: Malaysian CPG for Management of Colorectal Carcinoma, 2017).

  • Clinical One-Liner: Basically, it's a common and often silent cancer in our older population that you must suspect in any elderly patient with a change in bowel habits, unexplained anemia, or per-rectal bleeding.

II. Etiology & Risk Factors

  • Etiology: The majority of cases are sporadic, arising from the adenoma-carcinoma sequence over several years. About 20% have a familial component, and less than 5% are due to inherited syndromes like Lynch Syndrome (HNPCC) or Familial Adenomatous Polyposis (FAP).

  • Risk Factors (Malaysian Context):

    • Non-Modifiable:

      • Age > 50 years (though we are seeing it in younger patients).

      • Personal history of CRC or adenomatous polyps.

      • Family history of CRC.

      • Inflammatory bowel disease (Ulcerative Colitis > Crohn's Disease).

      • Inherited genetic syndromes (FAP, Lynch).

    • Modifiable:

      • Diet high in red and processed meats, low in fibre.

      • Obesity and a sedentary lifestyle.

      • Smoking.

      • Heavy alcohol consumption.

III. Quick Pathophysiology

Think of it as a multi-step process. It starts with a mutation in a single cell in the colon lining, often in the APC gene. This leads to a small, benign growth called a polyp. Over years, further mutations (e.g., in KRAS, TP53) accumulate, causing the polyp to grow, become dysplastic, and finally invade the bowel wall. This adenoma-to-carcinoma sequence is why screening by removing polyps is so effective. The tumour then spreads locally into the fat, invades lymph nodes, and metastasizes, usually to the liver and lungs.

IV. Clinical Assessment

  • Red Flags & Immediate Actions:

    • Large bowel obstruction (vomiting, absolute constipation, abdominal distension): → Alert senior immediately, keep patient nil by mouth (NBM), set up IV access, insert a Ryle's tube for decompression, get an urgent surgical review.

    • Perforation (peritonism, shock, fever): → This is a surgical emergency. Alert senior/surgical team, start fluid resuscitation with IV crystalloids, take urgent bloods including GXM, and prepare for emergency laparotomy.

    • Severe bleeding (hemodynamic instability, massive PR bleed): → Alert senior, secure two large-bore IV cannulas, start fluid resuscitation, send urgent FBC/GXM, and call for an urgent gastroenterology/surgical consult.

  • History:

    • Common (>50%): Change in bowel habit (constipation, diarrhea, or alternating), unexplained iron deficiency anemia, feeling of incomplete defecation (tenesmus), PR bleeding.

    • Less Common (10-50%): Abdominal pain/mass, unintentional weight loss.

    • Pertinent Negatives: Ask about NSAID use (to rule out PUD), history of IBD, and importantly, a detailed family history of any cancer.

  • Physical Examination:

    • General: Look for pallor (anemia), cachexia, and jaundice (liver metastasis).

    • Abdomen: Palpate for an abdominal mass (especially right-sided tumours) and hepatomegaly. Check for ascites.

    • Rectal Examination (DRE): Absolutely mandatory. You can feel a rectal tumour, assess its distance from the anal verge, its fixity, and check for blood on the glove.

  • Clinical Pearl: Don't attribute PR bleeding in an older patient to hemorrhoids without ruling out CRC. Any new iron deficiency anemia in a man or post-menopausal woman is CRC until proven otherwise.

V. Diagnostic Workflow

  • Differential Diagnosis:

    • Diverticular Disease:

      • Points For: Similar presentation with left lower quadrant pain, change in bowel habits, PR bleeding.

      • Points Against: Less likely to cause significant weight loss or profound anemia. Fever is more common.

      • How to Differentiate: Colonoscopy is key. CT scan can show diverticula and localised inflammation.

    • Inflammatory Bowel Disease (IBD):

      • Points For: Chronic diarrhea, PR bleeding, abdominal pain.

      • Points Against: Usually presents in a younger age group. May have extra-intestinal manifestations.

      • How to Differentiate: Colonoscopy with biopsy will show characteristic inflammatory changes, not malignancy.

    • Infective Colitis:

      • Points For: Acute onset of bloody diarrhea.

      • Points Against: Usually self-limiting, often associated with fever, recent travel or food history.

      • How to Differentiate: Stool culture. Symptoms usually resolve within a week.

  • Investigations Plan:

    • Bedside / Initial (First 15 Mins):

      • Digital Rectal Exam (DRE): Essential first step.

    • First-Line Labs & Imaging:

      • FBC: Look for microcytic anemia (Iron Deficiency Anemia).

      • Liver Function Test (LFT): Elevated ALP/GGT may suggest liver metastasis.

      • Renal Profile & Electrolytes: Baseline before contrast imaging and potential chemotherapy.

      • Carcinoembryonic Antigen (CEA): NOT for screening. Used as a baseline tumour marker before treatment and for surveillance after.

    • Confirmatory / Gold Standard:

      • Colonoscopy & Biopsy: This is the gold standard. It allows direct visualization of the entire colon, identification of the tumour, and tissue sampling for histology to confirm adenocarcinoma.

    • Staging Investigations:

      • CT Thorax, Abdomen, and Pelvis (CT-TAP): This is the workhorse for staging. It assesses the primary tumour (T-stage), involvement of regional lymph nodes (N-stage), and distant metastases (M-stage), especially in the liver and lungs.

VI. Staging & Severity Assessment

We use the TNM staging system (AJCC 8th Edition). As a house officer, you don't need to memorise the details, but you must understand the principles and what it means for management.

  • T (Tumour): How deep the tumour has invaded the bowel wall.

    • T1: Invades submucosa.

    • T4: Invades through the peritoneum or into other organs.

  • N (Nodes): Whether it has spread to nearby lymph nodes.

    • N0: No lymph node metastasis.

    • N1/N2: Spread to increasing numbers of regional lymph nodes.

  • M (Metastasis): Whether it has spread to distant organs.

    • M0: No distant metastasis.

    • M1: Distant metastasis (e.g., liver, lungs, peritoneum).

Direct Impact on Management:

  • Stage I-III (Localised): The goal is cure. This involves surgery, often followed by adjuvant chemotherapy for Stage III and high-risk Stage II to eliminate micrometastases.

  • Stage IV (Metastatic): The goal is usually palliative—to prolong life and maintain quality of life. Management involves systemic chemotherapy and sometimes targeted therapy or immunotherapy. Surgery may be considered for palliation of symptoms (like obstruction) or in select cases where metastases can be resected.

VII. Management Plan

Management is always discussed in a multidisciplinary team (MDT) meeting with surgeons, oncologists, and radiologists.

  • Immediate Stabilisation (The ABCDE Plan):

    • As mentioned under "Red Flags". Manage obstruction, perforation, or severe bleeding first. Resuscitate the patient.

  • Definitive Treatment (The Ward Round Plan):

    • Surgical Resection: This is the primary curative treatment for localised CRC. The aim is to remove the segment of the colon containing the tumour along with its draining lymph nodes (minimum 12 nodes needed for accurate staging).

      • Colon Cancer: Hemicolectomy (right or left), sigmoid colectomy, depending on location.

      • Rectal Cancer: More complex. Total Mesorectal Excision (TME) is the standard of care.

    • Adjuvant Chemotherapy (Post-surgery):

      • Stage III: Standard of care. Usually offered for 6 months.

      • High-Risk Stage II: May be considered, especially in younger patients with features like T4 tumours, perforation, or poorly differentiated histology.

      • Common Regimens in MOH: FOLFOX (5-FU, Leucovorin, Oxaliplatin) or CapeOx (Capecitabine, Oxaliplatin).

    • Metastatic Disease (Stage IV):

      • Palliative Chemotherapy: Combination chemotherapy (e.g., FOLFOX, FOLFIRI) is the mainstay.

      • Targeted Therapy: May be added based on molecular testing (e.g., Cetuximab for RAS wild-type left-sided tumours).

  • Long-Term & Discharge Plan:

    • Follow-up: Crucial for detecting recurrence. Patients are followed up for at least 5 years.

    • Surveillance Plan (as per CPG):

      • Clinic Review & CEA: Every 3-6 months for the first 2 years, then 6-monthly up to 5 years.

      • CT-TAP: Annually for the first 3 years, especially for high-risk patients.

      • Colonoscopy: At 1 year post-op. If normal, repeat in 3 years, then every 5 years.

VIII. Complications

  • Immediate (Post-Op):

    • Anastomotic Leak: Management: Alert senior immediately; may require IV antibiotics, radiological drain, or return to theatre.

    • Ileus: Management: Keep NBM, ensure adequate IV hydration and electrolyte correction.

  • Short-Term (Disease/Treatment Related):

    • Chemotherapy Side Effects (Neutropenia, Diarrhea, Neuropathy): Management: Depends on severity; may require G-CSF, anti-diarrheals, or dose modification by the oncologist.

  • Long-Term:

    • Recurrence (Local or Distant): Management: Re-staging and discussion at MDT for further treatment options (surgery, chemo, radiotherapy).

    • Stoma Complications (for patients with stomas): Management: Involve stoma nurse for skin care, education, and management of issues like retraction or parastomal hernia.

IX. Prognosis

Prognosis is directly related to the stage at diagnosis. This is why screening and early detection are vital.

  • 5-Year Survival Rate (Approximate):

    • Stage I: >90%

    • Stage II: 70-85%

    • Stage III: 50-70%

    • Stage IV: <15%

  • Top 3 Prognostic Factors: Stage at diagnosis (most important), tumour grade (differentiation), and presence of lymphovascular invasion.

X. How to Present to Your Senior

"Dr, for review please. This is [Patient's Name] in Bed [X], a [Age]-year-old [Gender] with [Relevant comorbidities], who presented with [Key symptom, e.g., three months of PR bleeding and anemia]. His hemoglobin is [Value]. I have performed a DRE which revealed [Findings, e.g., a hard, irregular mass 5cm from the anal verge]. My main differential is colorectal carcinoma. I have already sent off FBC, RP, LFT, and requested a baseline CEA. I would like to scope him. Could I get your opinion on the plan and urgency?"

XI. Summary & Further Reading

  • Top 3 Takeaways:

    1. Suspect CRC in any patient over 50 with anemia, PR bleeding, or a change in bowel habits.

    2. A digital rectal exam is a non-negotiable part of your initial assessment.

    3. The definitive diagnosis and staging are done via colonoscopy and CT scan, which guide the MDT management plan.

  • Key Resources:

Danial Mirza
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Gastric Cancer Clinical Overview