Abstract 989: Vitamin D and the modifying effect of body mass index on ovarian cancer recurrence
Authors: Jennifer A. Ritonja, Jérôme Laforme, Anita Koushik, HPROQ Study Team
Journal: Cancer Research (2025)

Abstract Purpose: Given the relatively poor survival associated with high-grade ovarian cancer, increasing knowledge of modifiable factors that improve prognosis is important. Higher vitamin D is associated with better prognosis in some cancers but its association with ovarian cancer remains unclear. Studies of individual vitamin D sources (e.g., diet, sun exposure) have reported null associations, yet they did not fully capture total vitamin D exposure. Studies of serum 25-hydroxyvitamin D (25(OH)D), a biomarker of total vitamin D exposure from all sources, show inconsistent results, although most assessed exposure prior to or during treatment, a period when symptoms, the cancer itself and therapies may influence 25(OH)D. Further, obesity is shown to modify associations between 25(OH)D levels and prognosis of some cancers, but no study has examined this specifically for ovarian cancer. Our objective was to examine 25(OH)D levels at 6 months post-treatment in relation to recurrence risk and explore the potential modifying effect of body mass index (BMI) in a cohort of individuals who had completed treatment for high-grade ovarian cancer. Methods: This prospective cohort study included 96 individuals diagnosed with high-grade epithelial ovarian cancer who remained responsive to platinum-based chemotherapy 6 months post-treatment. Information on vitamin D sources and lifestyle behaviors were self-reported at baseline and used to compute predicted levels of 25(OH)D using validated regression models. Cox proportional hazards regression was used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between predicted 25(OH)D (per 20 nmol/L increase) and recurrence risk. To examine whether associations varied by BMI, an interaction term was included in the regression model, with BMI categorized as normal (&amp;lt;25 kg/m2), overweight (25-29.9 kg/m2) or obese (≥30 kg/m2). Results: Overall, 49% of participants had a recurrence during follow-up (median: 1.5 years) and the mean predicted 25(OH)D level was 75.2 nmol/L (standard deviation: 15.9). 48% of participants had a normal BMI at baseline, while 28% and 24% were categorized as overweight or obese, respectively. For each 20 nmol/L increase in 25(OH)D, the HR (95% CI) for recurrence risk was 0.80 (0.52-1.12); after excluding participants who had a recurrence within 30 days of baseline the observed HR (95% CI) was stronger (0.68, 0.44-1.05). When examined according to BMI, a reduction in recurrence risk was observed among participants with a normal BMI (HR: 0.53; 95% CI: 0.29-0.96), but not those who had an overweight (HR: 0.92; 95% CI: 0.44-1.90) or obese (HR: 1.90; 95% CI: 0.56-6.42) BMI. Conclusions: Overall, our results suggest that higher predicted 25(OH)D may be associated with a reduced recurrence risk particularly among individuals with a normal BMI. This relationship should be explored further in research with larger sample sizes. Citation Format: Jennifer A. Ritonja, Jérôme Laforme, Anita Koushik, HPROQ Study Team. Vitamin D and the modifying effect of body mass index on ovarian cancer recurrence. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 989.