Colon Cancer Symptoms: Early Warning Signs & When to Screen

Recognizing Colorectal Cancer (CRC) Symptoms

Early CRC is often asymptomatic. Symptoms usually indicate advanced disease. Screening starting at age 45 (average risk) saves lives.

Common Symptoms

• Change in bowel habits: Persistent diarrhea, constipation, narrowing of stool (pencil-thin), tenesmus (urge without passage).
• Rectal bleeding / hematochezia: Bright red or dark blood mixed with stool. Not just on toilet paper.
• Abdominal discomfort: Cramping, pain, bloating, fullness.
• Unexplained weight loss.
• Fatigue/weakness: From chronic blood loss → iron deficiency anemia.
• Iron deficiency anemia (men/postmenopausal women): Often first sign of right-sided colon cancer.

Red Flags for Urgent Evaluation

• Age ≥45 (or ≥40 with family history).
• Rectal bleeding + change in bowel habits >2 weeks.
• Palpable abdominal mass.
• Unexplained iron deficiency anemia.

Screening Modalities (USPSTF/ACS)

Test	Frequency	Pros	Cons
Colonoscopy	10 yr	Gold standard; detects & removes polyps; full visualization	Prep, sedation, perforation risk (rare), cost
FIT (Fecal Immunochemical Test)	Annual	Non-invasive, no prep, low cost	Misses some polyps; positive → colonoscopy needed
Cologuard (mt-sDNA)	3 yr	Non-invasive, detects DNA + blood	Higher false +; positive → colonoscopy
CT Colonography	5 yr	Non-invasive, visualizes extracolonic	Prep, radiation, positive → colonoscopy
Flexible Sigmoidoscopy	5 yr (+ FIT annual)	Less prep, no sedation	Only distal colon; misses proximal

Risk Factors

• Age, family history (1st degree relative <60 or 2+ relatives), personal history of polyps/IBD (Crohn's/UC), Lynch syndrome/FAP, obesity, smoking, alcohol, red/processed meat, low fiber, sedentary.

Don't wait for symptoms. Talk to your doctor about the right screening test for you.