Body Mass Index and PSA Failure Following Brachytherapy for Localized Prostate Cancer

Abstract

Greater body mass index (BMI) is associated with shorter time to prostate-specific antigen (PSA) failure following radical prostatectomy and external beam radiation therapy (EBRT) with or without androgen deprivation therapy (ADT). We investigated whether BMI is associated with time to PSA failure in a cohort of men treated with permanent prostate brachytherapy for clinically localized prostate cancer. A retrospective analysis was conducted on 374 consecutive patients who underwent brachytherapy with or without supplemental EBRT and/or ADT for clinical stage T1c-T2c NX M0 prostate cancer between August 1996 and December 2001 and who had a minimum follow-up of 3 years. Forty-nine (13%) of these patients received supplemental EBRT and 131 (35%) received ADT, while 207 (55.4%) were treated with brachytherapy only. Height and weight data were available at baseline for 353 (94%) of the men. Cox regression analyses were performed to evaluate the relationship between BMI and time to PSA failure (nadir + 2 ng/ml definition). Covariates included age, race, pre-implant PSA level, Gleason score, T-category, use of supplemental EBRT, and use of ADT. Median age, PSA, and BMI at baseline were 66 (range 42–80) years, 5.7 (range 0.4–22.6) ng/ml, and 27.1 (range 18.2–53.6) kg/m2, respectively. After a median follow-up of 6.0 (range 3.0–10.2) years, there were a total of 76 PSA failures. BMI was not associated with PSA failure. At 6-years, the PSA failure rate was 30.2% for men with BMI < 25 kg/m2, 19.5% for men with BMI ≥25–<30, and 14.4% for men with BMI ≥30 (p = 0.19). Results were similar when BMI was analyzed as a continuous variable, when using alternative definitions of PSA failure, and when excluding patients treated with EBRT and/or ADT. In multivariate analyses, only baseline PSA was significantly associated with shorter time to PSA failure [adjusted HR 1.12, 95% CI 1.05–1.20, p = 0.0006] (Table). Unlike following surgery or EBRT, a greater baseline BMI is not associated with higher PSA failure rates in men treated with brachytherapy for clinically localized prostate cancer. This raises the possibility that brachytherapy may be a preferred treatment strategy for obese patients.TableMultivariate Analysis of PSA Failure using Nadir +2 Definition (n = 350)CovariateAdjusted HR [95% CI]p-valueBMI (kg/m2) <25—— ≥25–<300.76 [0.45–1.29]0.31 ≥300.56 [0.29–1.10]0.091Baseline PSA (ng/ml), continuous1.12 [1.05–1.20]0.0006Gleason score ≤6—— 71.64 [0.91–2.96]0.099 8–100.94 [0.22–4.00]0.93Tumor category T1—— T20.81 [0.45–1.43]0.46EBRT No—— Yes1.12 [0.56–2.23]0.75ADT No—— Yes1.11 [0.68–1.83]0.68Race Black—— Other0.49 [0.22–1.07]0.073 Open table in a new tab