- Colorectal cancer (CRC) location is tied to risk for second primary gastrointestinal (GI) malignancies in specific locations.
Why this matters
- CRC history is already a known risk factor for second primary GI cancer, but location-specific risks are not as clear.
- 30.3% had right-sided, 35.3% left-, 34.3% rectal first primary CRC (all higher than average).
- 4.3% developed second primary GI cancer (64% CRC; 36% not).
- Primary at any location was tied to:
- increased risk for small intestine cancer (standardized incidence ratio [SIR], 2.95 [95% CI, 2.82-3.08]),
- bile duct cancer (1.29 [1.22-1.36]), and
- other CRCs (multiple locations); but
- decreased liver (0.78 [0.74-0.82]), gallbladder (0.65 [0.59-0.72]) cancer risk.
- Right-sided primary CRC was tied to increased small intestine (SIR, 4.06 [95% CI, 3.78-4.36), pancreatic (1.14 [1.09-1.19]) malignancy risk vs left/rectal initial locations.
- Left-sided was linked to increased esophageal cancer risk (SIR, 1.16 [95% CI, 1.08-1.24]).
- Pancreatic cancer risk was decreased with left-sided/rectal primary initial location.
- Retrospective study; 281,413 patients with CRC (42% localized).
- Median follow-up, 4.9 years.
- Funding: None disclosed.
- Retrospective; some medical record misclassification should be assumed.
- Information on crucial risk factors (e.g., family history, IBD) unavailable.
- Follow-up possibly too short to capture some cases.