2309: The Influence of Body Mass Index on PSA Failure Following Androgen Suppression and Radiation Therapy for Localized Prostate Cancer

Abstract

Increasing body mass index (BMI) has been shown to be associated with a shorter time to prostate specific antigen (PSA) failure following radical prostatectomy. We investigated whether BMI is associated with time to PSA failure in men treated with radiation therapy (RT) and androgen suppression therapy (AST) for clinically localized prostate cancer. Between December 1995 and April 2001, 102 of 206 men with clinically localized prostate cancer, enrolled on a prospective randomized trial, received 70 Gy 3-dimensional conformal RT with 6 months of AST. Height and weight data were available at randomization for 99 of the 102 (97%) men and from which BMI was calculated. Adjusting for age (continuous) and the known prognostic factors including the PSA level (continuous), Gleason score (GS) and T-category, Cox regression analyses were performed to analyze whether BMI (continuous) was associated with time to PSA failure (PSA>1.0 ng/ml and increasing >0.2 ng/ml on 2 consecutive visits). The median age and median BMI [interquartile range (IQR)] at randomization was 72 (69.1 to 74.7) years and 27.4 (24.8 to 30.7) kg/m2, respectively. As shown in the Table, in addition to an increasing PSA level (p=0.006) and Gleason 8 to 10 cancer (p=0.024), after a median follow-up (IQR) of 6.9 (5.6 to 8.5) years, an increasing BMI was also significantly associated with a shorter time to PSA failure [adjusted hazard ratio (HR) 1.10; 95% confidence interval (CI) 1.01 to 1.19; p=0.026] following RT and AST.Tabled 1CovariateNo. MenPSA FailureNo. EventsUVAMVAHR [95% CI]P-ValueHR [95% CI]P-ValueBMI (continuous)99251.11 (1.02, 1.20)0.0181.10 (1.01, 1.19)0.026PSA (continuous)99251.06 (1.02, 1.11)0.0041.07 (1.02, 1.13)0.006Age (continuous)99250.94 (0.87, 1.01)0.0860.98 (0.91, 1.06)0.624GS 6 or less3381.0—1.0—GS 756120.88 (0.36, 2.15)0.7771.36 (0.46, 4.0)0.580GS 8 to 101052.56 (0.84, 7.85)0.0994.35 (1.22, 15.5)0.024T154101.0—1.0—T245152.14 (0.96, 4.78)0.0621.69 (0.73, 3.94)0.223UVA: univariable analysis; MVA: multivariable analysis. Open table in a new tab UVA: univariable analysis; MVA: multivariable analysis. After adjusting for known prognostic factors, baseline BMI is significantly associated with time to PSA failure following RT and AST for men with clinically localized prostate cancer. Further study is warranted to assess the impact of an increasing BMI following AST administration on PSA failure, prostate cancer-specific and all-cause mortality.