Abstract 2585: Dietary isoflavone intake and lung cancer risk: an analysis using data from the prostate, lung, colorectal, and ovary (PLCO) trial

Introduction: Dietary isoflavones are mainly from soy-based foods and are widely consumed in Asian countries. Isoflavone has a similar chemical structure to estrogen and has been suggested to decrease the risk of breast cancer by acting as an estrogen antagonist. Lung cancer development was also suggested to be affected by estrogen signaling. We aim to explore isoflavone intake and lung cancer risk using the prospective PLCO trial. Methods: Data regarding dietary intake using the food frequency questionnaire, demographic and reproductive information and lung cancer diagnosis were extracted. The associations between lung cancer risk and isoflavone intake (in quartiles) overall and stratified by gender and smoking status were calculated using the Cox proportional hazard models adjusting for potential confounders. SAS 9.4 were used to perform all statistical analyses. Results: During the 1,215,948 person-year follow-up, a total of 1,706 lung cancer cases were diagnosed. Overall (Table), the highest quartile of isoflavone intake was associated with 26% reduced risk of lung cancer compared to the lowest quartile. When the analysis was stratified by gender and further by smoking status (never vs ever), the decreased risk was only observed among male ever smokers (Q4 vs Q1: HR=0.78, 95%CI: 0.64-0.96) but not their female counterparts (Q4 vs Q1: HR=0.85, 95%CI: 0.68-1.08). Discussion: This is the first prospective cohort study investigating isoflavone intake and lung cancer risk and we found a protective effect of isoflavone intake against lung cancer risk particularly among male ever smokers, despite an overall lower isoflavone intake among the US populations compared to the Asian populations. Future studies are needed to replicate these results in independent cohorts and shed a light on the potential mechanism of the protective effect of isoflavones on lung carcinogenesis and the interactions between isoflavones, smoking and endogenous estrogens. Citation Format: Qian Wang, Meng Ru, Paolo Boffetta. Dietary isoflavone intake and lung cancer risk: an analysis using data from the prostate, lung, colorectal, and ovary (PLCO) trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 2585.