Body mass index and ampulla of Vater cancer incidence and survival: a cohort study of 1.7 million Norwegians

BACKGROUND: Although higher body mass index (BMI) has been associated with increased risk of hepatobiliary cancers in previous studies, the association with risk of ampulla of Vater cancer has rarely been reported. We therefore investigated the association between BMI and ampulla of Vater cancer incidence in a large Norwegian cohort. METHODS: The analytical dataset included 1,723,692 men and women aged 16-75 years at baseline in 1963-1975. Multivariable Cox regression analyses were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between BMI and ampulla of Vater cancer incidence and survival. RESULTS: During 56.1 million person-years of follow-up, a total of 814 cases with ampulla of Vater cancer were identified. Compared to participants with a BMI of 18.5-<25 kg/m², the HRs (95% CIs) of those with a BMI of 15-<18.5, 25-<30, and ≥30 kg/m² were 0.19 (0.05-0.77), 1.02 (0.88-1.19), and 1.03 (0.80-1.32), respectively, and 1.02 (0.92-1.12) per 5 kg/m² increment. No association was observed in men and women, when analysed separately. The HRs (95% CIs) for BMI in young adulthood were 0.39 (0.10-1.57), 1.00, 1.26 (0.80-1.99), and 3.62 (1.76-7.48, Ptrend=0.004) for a BMI of 15-<18.5, 18.5-<25.0, 25-<30, and ≥30 kg/m², and 1.61 (1.25-2.06) per 5 kg/m² increment (n=130), and for early-onset ampulla of Vater cancer (n=19) was 1.00, 2.10 (0.75-5.88), and 5.45 (1.16-25.70, Ptrend=0.01), and 1.91 (1.10-3.32) per 5 kg/m² increment. Higher BMI was not clearly associated with cancer-specific survival among ampulla of Vater cancer patients (HR 1.19, 95% CI: 0.89-1.61 for BMI ≥30 vs. 18.5-<25.0 kg/m²). CONCLUSIONS: Overall, the results show no clear association between higher BMI and ampulla of Vater cancer incidence or survival. However, strong positive associations were observed between BMI in young adulthood and risk of ampulla of Vater cancer and between BMI and early-onset diagnosis. Further studies are needed to verify these findings.