Abstract LB-179: Pre- and post-diagnosis body mass index, weight change, and prostate cancer-specific mortality among prostate cancer survivors in the US

Abstract

Abstract Accumulating evidence suggests that excess body fatness is associated with an increased risk of aggressive prostate cancer. However, the roles of body mass index (BMI -kg/m2), reported before and after diagnosis, and weight change in long-term prostate cancer survival remain unclear. Prospective data from men diagnosed with non-metastatic prostate cancer between 1992 and 2013 were obtained from the American Cancer Society’s Cancer Prevention Study II Nutrition Cohort. Weight was self-reported on surveys completed at enrollment into the Nutrition Cohort in 1992, in 1997, and every 2 years thereafter. Pre-diagnosis BMI was from the first survey completed >1 year before diagnosis and post-diagnosis BMI from the first survey completed > 2 years after diagnosis to allow for treatment completion. BMI was classified as ideal (18.5-<25), overweight (25-<30), and obese (30+). Weight change was the difference in weight (lbs.) from pre- to post-diagnosis. Follow-up began on the date of diagnosis in pre-diagnosis analyses (n=9,867) and, to reduce the potential for reserve causation, 4-years after the post-diagnosis survey in post-diagnosis analyses (n=6,860). Follow-up ended at death or December 2014, whichever came first. Cox proportional hazard models were used to estimate cause-specific hazard ratios (HR) and 95% confidence intervals (95% CI), adjusted for age, race, education, initial treatment, stage, Gleason score, node involvement, comorbidities, pre-diagnosis BMI (weight change models only), smoking, alcohol, and physical activity. A total of 614 and 330 prostate cancer deaths occurred in the pre- and post-diagnosis cohorts, respectively. The median follow-up time was 10.6 years (interquartile range (IQR) =7.9) and 5.5 years (IQR=6.1) in the pre- and post-diagnosis cohorts, respectively. In pre-diagnosis multivariable models, BMI was not associated with prostate cancer-specific mortality (e.g., Obese vs Ideal: HR=1.09, 95% CI: 0.83, 1.42). In post-diagnosis models, compared to men with an ideal BMI, the hazard of prostate cancer-specific death was similar among overweight men (HR=1.08, 95%CI: 0.84, 1.39) and higher among obese men (HR=1.41, 95% CI: 1.02, 1.97). Compared to men who maintained their weight (± 5 lbs.), the hazard of prostate cancer-specific mortality was higher among men who gained > 10 lbs. (HR=1.33, 95%CI: 0.99, 1.77) or lost > 10 lbs. (HR=1.33, 95%CI: 0.92, 1.92), but was similar among men who gained or lost 5-10 lbs. Our results suggest that post-diagnosis obesity and weight gain may be associated with increased risk of prostate cancer-specific mortality. The suggestion of an inverse association between weight loss and higher prostate cancer-specific mortality in our study should be interpreted with caution as it is unknown whether weight loss occurring was intentional or due to advanced disease. Citation Format: Alyssa N. Troeschel, Eric J. Jacobs, W. Dana Flanders, Victoria L. Stevens, Terryl J. Hartman, Lauren E. McCullough, Ted Gansler, Ying Wang. Pre- and post-diagnosis body mass index, weight change, and prostate cancer-specific mortality among prostate cancer survivors in the US [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr LB-179.