Colorectal Cancer: Clinical Manifestations, Diagnosis, and Management
Introduction
Colorectal cancer (CRC) includes malignancies of the colon and rectum. Presentation varies by tumor location and stage. Early recognition of symptoms, appropriate use of diagnostic tools, and timely treatment significantly improve outcomes.
Contents
Clinical Manifestations
Colon Cancer
- Bowel habit changes: increased frequency, alternating diarrhea/constipation, change in stool caliber.
- Stool abnormalities: overt or occult blood, mucus.
- Abdominal pain: persistent dull ache or cramping; colicky pain with partial obstruction.
- Palpable mass: firm, nodular mass; may represent tumor or fecal loading proximal to obstruction.
- Systemic symptoms: iron‑deficiency anemia, fatigue, weight loss, low‑grade fever due to chronic blood loss and inflammation.
Rectal Cancer
- Often asymptomatic early; bleeding may be microscopic.
- Rectal irritation: tenesmus, sensation of incomplete evacuation, frequent urges, diarrhea.
- Bleeding/infection: blood and mucus coating stool; purulent discharge with ulcerated/infected lesions.
- Stenosis/obstruction: progressive narrowing of stool caliber, abdominal distension, pain, and constipation as lumen narrows.
Diagnostic Evaluation
- History and physical: characterize bleeding, bowel habit changes, weight loss; digital rectal exam; assess for iron‑deficiency anemia.
- Laboratory tests: CBC, iron studies; CEA baseline once cancer is confirmed.
- Colonoscopy: diagnostic gold standard with biopsy and opportunity for polypectomy of synchronous lesions.
- Imaging: CT chest/abdomen/pelvis for staging; MRI pelvis for rectal tumors; endorectal ultrasound for early rectal lesions; CT colonography if colonoscopy incomplete.
- Pathology: confirm adenocarcinoma; assess mismatch repair (MMR) by IHC or MSI for Lynch screening and prognosis.
Staging (AJCC TNM)
- T: depth of invasion through bowel wall.
- N: number of involved regional lymph nodes.
- M: distant metastasis (liver, lung, peritoneum, etc.).
Management Overview
Colon Cancer
- Localized disease: oncologic resection with adequate margins and ≥12 lymph nodes; adjuvant chemotherapy for stage III and selected high‑risk stage II.
- Complications: manage obstruction (stent as bridge to surgery vs urgent resection), perforation, bleeding.
Rectal Cancer
- Local staging with high‑resolution pelvic MRI is essential.
- cT3/4 or node‑positive: total neoadjuvant therapy (chemoradiation + systemic chemotherapy) followed by total mesorectal excision (TME).
- Early T1 lesions: local excision if favorable; otherwise TME.
- Organ preservation: selective non‑operative management (watch‑and‑wait) for complete clinical responders in experienced centers.
Metastatic Disease
- Comprehensive molecular profiling (RAS/RAF, HER2, MSI/dMMR) to guide targeted therapy and immunotherapy.
- Systemic therapy: fluoropyrimidine‑based combinations (FOLFOX, CAPOX, FOLFIRI) ± biologics (anti‑VEGF; anti‑EGFR for left‑sided RAS wild‑type).
- Oligometastatic: consider resection/ablation of liver or lung metastases within MDT planning.
Surveillance and Prevention
- Post‑treatment surveillance: periodic history/physical, CEA, CT imaging, and colonoscopy per stage‑based guidelines.
- Screening: begin at age 45 for average‑risk adults (colonoscopy q10y, annual FIT, FIT‑DNA q3y, CT colonography q5y, flexible sigmoidoscopy q5–10y). Positive stool tests require diagnostic colonoscopy.
- Risk reduction: healthy diet, physical activity, weight management, limit alcohol, avoid smoking; aspirin chemoprevention for select high‑risk patients after individualized risk–benefit discussion.
Red Flags Requiring Urgent Evaluation
- Overt rectal bleeding with anemia, signs of obstruction (severe abdominal pain, vomiting, obstipation), or unexplained iron‑deficiency anemia.
Key Takeaways
- Symptoms depend on tumor site; right‑sided cancers often present with anemia, left‑sided with change in caliber/obstruction, rectal with bleeding/tenesmus.
- Colonoscopy with biopsy remains the diagnostic gold standard; MRI is pivotal for rectal staging.
- Stage‑ and biology‑driven therapy, with MDT coordination, optimizes outcomes.