79P Plant-based diet indices and their interaction with ambient air pollution on the ovarian cancer survival: A prospective cohort study

Ambient air pollution might serve as a prognostic factor for ovarian cancer (OC) survival, yet the relationships between plant-based diet indices (PDIs) and OC survival remained unclear. We aimed to investigate the associations of comprehensive air pollution and PDIs with OC survival and explored the effects of air pollution-diet interactions. The present study encompassed 658 patients diagnosed with OC. The overall plant-based diet index (PDI), the healthful PDI, and the unhealthful PDI (uPDI) were evaluated by a self-reported validated food frequency questionnaire. In addition, an air pollution score (APS) was formulated by summing the concentrations of particulate matter with a diameter of 2.5 microns or less, ozone, and nitrogen dioxide. Cox proportional hazard models were applied to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) of overall survival (OS). The modifying effect of PDIs on the relationships between APS and OS was further examined by incorporating interaction terms. Throughout a median follow-up of 37.60 (interquartile: 24.77–50.70) months, 123 deaths were confirmed. Comparing extreme tertiles, higher uPDI was associated with lower OS of OC (HR=2.06, 95%CI=1.30, 3.28; P-trend<0.01), whereas no significant association was found between overall PDI as well as hPDI and OC survival (P-trend>0.05 for both). Higher APS (HR for per interquartile range=1.27, 95%CI=1.01, 1.60) were significantly associated with worse OC survival, and the associations could be exacerbated by adhering to uPDI. Notably, an additive interaction was identified between combined air pollution and uPDI (P < 0.005 for high APS and high uPDI). We also found that adherence to overall PDI aggravated associations of air pollution with OC survival (P-interaction=0.006). Joint exposure to various ambient air pollutants was significantly associated with lower survival among patients with OC, particularly for those who predominantly consumed unhealthy plant-based food.