Abstract 591: Circulating testosterone in modifying the association of BMI change rate with serum PSA in prostate cancer-free men with initial-PSA less than 4 ng/mL
Authors: Wang Kai , Prosperi Mattia , Qiu Peihua , Cheng Ting-Yuan David , Bird Victoria Y. , Chen Xinguang , Song Mingyang 
Published: August 2019

Abstract
Background: Body mass index (BMI)-adjusted prostate-specific antigen (PSA) model has been proposed to improve the predictive accuracy of serum PSA in prostate cancer (PCa) screening. However, how BMI change rate may influence PSA levels in PCa-free men has not been well studied. The current study is to examine the relationship between BMI change rate and serum PSA in PCa-free men and whether this relationship is modified by circulating testosterone.
Methods: We conducted this study at a tertiary hospital in the Southeastern US using the Electronic Medical Records of PCa-free men with initial PSA less than 4 ng/mL (cutoff for prostate biopsy), at least 1 testosterone measurement and at least 2 BMI measurements during the study period. Time when the first BMI measurement was recorded served as the baseline, and the study period was defined from baseline to the most recent hospital visit. The included medical records ranged from Jun 2001 to Oct 2015. BMI change rate was created in two ways depending on the number of data points. For men with only 2 BMI measurements, it was calculated by firstly subtracting baseline BMI from the second BMI, then dividing the difference by time interval (months) between the two BMI measurements. For men with more than 2 BMI measurements, we firstly regressed BMI to time interval (months) between that measurement and baseline, then took the β regression coefficient (slope) as the BMI change rate for that men. Multivariable linear regression was used to assess the association of BMI change rate with three PSA measures, including peak, the most recent, and mean PSA during the study period. Effect modification by testosterone was assessed through stratified analysis by testosterone level of 280 ng/dL as cutoff.
Results: A total of 470 men with a mean study period of 97.6 months were included. Median age at baseline was 62 years. After adjusting for covariates including baseline BMI, no significant association of BMI change rate was observed with peak PSA (β =0.416, P =0.078), the most recent PSA (β =0.360, P =0.139), or mean PSA (β =0.405, P =0.064) in the overall sample. However, testosterone-stratified analyses indicated that BMI change rate was positively associated with peak PSA (β =1.118, P =0.013), the most recent PSA (β =0.932, P =0.044), and mean PSA (β =1.034, P =0.013) in men with testosterone &lt;280 ng/dL, but no significant association was observed in men with testosterone ≥280 ng/dL (for peak PSA, β =0.076, P =0.785; for the most recent PSA, β =0.072, P =0.802; for mean PSA, β =0.099, P =0.700).
Conclusion: Accelerated BMI increase in middle-to-late adulthood might correlate with higher PSA level if a low circulating testosterone occurred concurrently. Further studies are needed to confirm this finding.
Citation Format: Kai Wang, Mattia Prosperi, Peihua Qiu, Ting-Yuan David Cheng, Victoria Y. Bird, Xinguang Chen, Mingyang Song. Circulating testosterone in modifying the association of BMI change rate with serum PSA in prostate cancer-free men with initial-PSA less than 4 ng/mL [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 591.