What are the typical presentation, diagnosis, management, and complications of colon cancer?

Colon Cancer: Presentation, Diagnosis, Management, and Complications

Colon cancer typically presents with change in bowel habits, abdominal pain, weight loss, weakness, iron deficiency anemia, and rectal bleeding, with dark red rectal bleeding and abdominal mass having >95% specificity for colorectal cancer diagnosis. 1

Typical Presentation (Signs and Symptoms)

Common Symptoms

• Change in bowel habits (present in 51% of cases) 2
• Rectal bleeding (58% of cases) - most common and strongest association with diagnosis 2
• Abdominal pain (52% of cases) - general or localized 1, 2
• Weight loss without other specific causes 1
• Weakness and fatigue 1
• Iron deficiency anemia (57% of cases) 2

High-Specificity Findings

• Dark red rectal bleeding (>95% specificity) 1
• Palpable abdominal mass (>95% specificity) 1

Symptom Combinations

• Multiple symptoms increase diagnostic probability:
  • One red-flag symptom increases risk by 1.9-fold
  • Two symptoms increase risk by 3.6-fold
  • Three or more symptoms increase risk by 6.5-fold 3

Differential Diagnosis

The differential diagnosis for colon cancer includes:

• Inflammatory bowel disease
• Irritable bowel syndrome
• Diverticular disease
• Hemorrhoids
• Infectious colitis
• Ischemic colitis
• Small intestinal bacterial overgrowth 4
• Bile acid malabsorption 4

Diagnostic Workup

Initial Evaluation

1. Complete colonoscopy - gold standard for diagnosis 1

   • Allows for direct visualization, biopsy, and removal of polyps
   • Identifies tumor location and detects synchronous lesions

2. Laboratory tests 1

   • Complete blood count (anemia assessment)
   • Liver and kidney function tests
   • Serum albumin
   • Carcinoembryonic antigen (CEA) - baseline for monitoring

3. Imaging studies 1

   • CT scan of abdomen and pelvis
   • Chest X-ray
   • Liver ultrasound (if CT unavailable)

When Complete Colonoscopy Cannot Be Performed

• Limited left-sided colonoscopy with barium enema
• CT colonography (virtual colonoscopy)
• Complete colonoscopy should be performed within 3-6 months after surgery if not done preoperatively 1

Pathological Assessment

The standard pathological assessment should include 1:

• Morphological description of specimen
• Surgical procedure performed
• Tumor site and size
• Presence/absence of macroscopic perforation
• Histological type and grade
• Extension of tumor (T stage)
• Distance from resected margins
• Presence/absence of tumor deposits
• Lymphovascular/perineural invasion
• Tumor budding
• Lymph node status (N stage)
• Metastatic involvement (M stage)

Management

Surgical Management

1. Localized disease (Stage I-III)

   • Colectomy with en bloc removal of regional lymph nodes 1
   • For obstructing tumors: resection with diversion or stent insertion followed by colectomy 1
   • For unresectable tumors: diverting colostomy followed by palliative resection 1

2. Metastatic disease (Stage IV)

   • For resectable liver metastases: colectomy followed by liver resection or colectomy with neoadjuvant chemotherapy and staged liver resection 1
   • For limited lung metastases (1-3 nodules): colectomy with lymph node removal followed by pulmonary nodule resection 1
   • For unresectable metastases: limited colon resection followed by systemic therapy 1

Adjuvant Therapy

1. Stage III (node-positive)

   • 6 months of 5-fluorouracil (5-FU) plus leucovorin adjuvant chemotherapy (category 1 recommendation) 1

2. Stage II

   • Not considered standard but may be considered for high-risk features:
     • Grade 3 or 4 lesions
     • Lymphatic/vascular invasion
     • Bowel obstruction 1

3. Stage IV with resected metastases

   • 4-6 months of adjuvant chemotherapy
   • Options include:
     • Systemic 5-FU plus leucovorin
     • 5-FU plus leucovorin plus oxaliplatin
     • Continuous-infusion 5-FU
     • 5-FU plus leucovorin plus irinotecan 1

Palliative Therapy for Metastatic Disease

• First-line: 5-FU in various combinations and schedules 1
• Second-line: oxaliplatin or irinotecan for selected patients with good performance status 1
• Locoregional chemotherapy may be considered for liver metastases only 1

Complications

1. Local complications

   • Bowel obstruction
   • Perforation
   • Bleeding
   • Fistula formation

2. Metastatic complications

   • Liver metastases (most common)
   • Lung metastases
   • Peritoneal carcinomatosis

3. Treatment-related complications

   • Surgical: anastomotic leak, wound infection, adhesions
   • Chemotherapy: nausea, vomiting, diarrhea, neutropenia, neuropathy

4. Long-term complications

   • Chronic bowel dysfunction
   • Metachronous primary tumors (up to 3% during 5 years after surgery, increasing to 9% after several decades) 1

Screening and Surveillance

Screening Recommendations

• Age range: 50-74 years 1
• Options:
  • Colonoscopy every 10 years (optimal age for single colonoscopy: around 55 years) 1
  • Flexible sigmoidoscopy every 5-10 years 1
  • Fecal immunochemical test (FIT) annually 1

Post-Treatment Surveillance

• Complete colonoscopy within 3-6 months after surgery if not done preoperatively 1
• Regular monitoring of CEA levels 1
• Symptom-driven visits are recommended 1

Clinical Pearls and Pitfalls

Pearls

• Non-distal rectal bleeding has higher positive predictive value (22%) for colon cancer than distal rectal bleeding (2.1%) 5
• Age ≥50 years significantly increases the positive predictive value of symptoms 5
• The presence of weight loss accompanying rectal bleeding increases the likelihood of colorectal cancer 6

Pitfalls

• Dismissing symptoms in younger patients (<45 years) as the incidence of early-onset colorectal cancer is increasing 3
• Using fecal immunochemical test (FIT) for symptomatic patients may delay diagnosis 3
• Relying on single symptoms like constipation, diarrhea, or abdominal pain alone, which have low positive predictive values 5, 7
• Failing to recognize that symptoms may precede diagnosis by a median of 14 weeks 2