Supplementary Material for: Risk Factors for Rectal Neuroendocrine Tumors: A Population-Based Cohort Study of Sex-Specific Associations

BACKGROUND: Risk factors for rectal neuroendocrine tumors (NETs) have not been reported in a cohort setting, although their association has been reported in cross-sectional studies. We investigated the sex-specific risk factors for rectal NETs.
SUBJECTS/METHODS: In this population-based cohort study, individuals without previously diagnosed cancer and NETs who underwent general health examinations and cancer screenings in 2010 were enrolled and followed through 2017.
RESULTS: Among 5.521 million, 2,342 patients with rectal NETs were identified. In the adjusted analysis, male sex (adjusted hazard ratio [aHR] 1.27; 95% confidence interval [CI] 1.12–1.43), current smokers (aHR 1.15), past smokers (aHR 1.16), and obesity (aHR 1.50; 95% CI 1.03–2.20) were associated with an increased risk of rectal NETs. Frequent alcohol consumption was associated with an increased risk of rectal NETs in a dose-dependent manner (aHR 1.37 for 1/week, 1.49 for 2–3/week, and 1.56 for 4–5/week). In men, current smokers, frequent alcohol consumption, and obesity (HR 2.63; 95% CI 1.44–4.80) were associated with an increased risk of NETs, and waist circumference was associated with rectal NETs in a dose-dependent manner (P for trend < 0.001). In women, past smokers (aHR 1.76) and alcohol consumption were associated with rectal NETs. Younger age was associated with rectal NET risk in men and women.
CONCLUSION: Younger age, smoking, and frequent alcohol consumption were associated with increased risk of rectal NETs in both men and women, whereas obesity showed a strong association with increased risk in men but not in women. Due to observational study, causality cannot be inferred.