Abstract 944: Total body composition and the association with high-grade prostate cancer

Abstract

Abstract Background: Prostate cancer remains a leading cause of cancer death. Several studies suggest that obesity increased risk of advanced prostate cancer. However, research is inconsistent, perhaps because BMI is known to be associated with prostate cancer detection or because BMI is less valid as an estimate of body fat content among older men. We investigated the association between high-grade prostate cancer and total body fat mass, lean mass, and percent fat (% body fat) measured by bioelectrical impedance analysis (BIA), in addition to BMI, waist circumference, and waist-hip ratio (WHR). Our results may help to better understand how obesity affects prostate cancer. Methods: The Nashville Men's Health Study was designed to investigate the associations between obesity and prostate cancer, while controlling for differences in prostate cancer detection. Men less than 40 years, with a prior prostate cancer diagnosis, taking hormone supplementation or a steroid reductase inhibitor, or unable to speak English were excluded. Approximately 95.5% of eligible men consented to participate. All body size measures were ascertained prior to prostate biopsy or diagnosis, by trained research staff. Clinical and screening histories and biopsy pathology were abstracted from medical reports. High-grade prostate cancer (n=332) was defined as a Gleason score greater than six. Controls (n=871) included men without low-grade cancer, PIN, or other suspicious findings at biopsy, minimizing bias due to latent cancer and allowing identical data collection to cases. Multivariable logistic regression was used to determine the association between body composition and prostate cancer, while adjusting for age, prostate size, number of biopsy cores collected, race, and family history. Results: High-grade prostate cancer was significantly associated with BMI (continuous: OR=1.023, 95% CI=(1.001, 1.046), p=0.025), waist circumference ((cm), OR=1.012, 95% CI=(1.002, 1.023), p=0.002), total fat mass ((kg), OR=1.013, 95% CI=(1.003, 1.024), p=0.015), and total lean mass ((kg), OR=1.038, 95% CI=(1.020, 1.056), p<0.001). High grade prostate cancer was not significantly associated with WHR or % body fat. When obesity scores were categorized, high-grade prostate cancer was significantly associated with a BMI of 30 or more (OR=1.43, 95% CI=(1.07,1.91), and with a total body fat mass (OR=1.35, 95% CI=(1.02, 1.77) and total lean mass (OR=1.80, 95% CI=(1.35, 2.40)) above the median. BMI was correlated with body fat mass (r=0.90) and lean body mass (r=0.60). Furthermore, BMI was not associated with prostate cancer after controlling for total lean body mass (BMI: OR=0.993 (0.960, 1.028); Lean Mass: OR=1.040, 95% CI=(1.018, 1.064)). Conclusion: Lean body mass may mediate the association between prostate cancer and BMI. Factors that influence maintenance of lean body mass, such as testosterone or IGF, may underlie this association. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 944. doi:10.1158/1538-7445.AM2011-944