Abstract LB-179: Pre- and post-diagnosis body mass index, weight change, and prostate cancer-specific mortality among prostate cancer survivors in the US
Authors: Troeschel Alyssa N. , Jacobs Eric J. , Flanders W. Dana , Stevens Victoria L. , Hartman Terryl J. , McCullough Lauren E. , Gansler Ted , Wang Ying 
Published: August 2019

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 &gt;1 year before diagnosis and post-diagnosis BMI from the first survey completed &gt; 2 years after diagnosis to allow for treatment completion. BMI was classified as ideal (18.5-&lt;25), overweight (25-&lt;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 &gt; 10 lbs. (HR=1.33, 95%CI: 0.99, 1.77) or lost &gt; 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.