Influence of body mass index on biochemical outcome after permanent prostate brachytherapy.

OBJECTIVES: To evaluate the impact of body mass index (BMI) on the 8-year biochemical outcome after permanent prostate brachytherapy with or without the addition of supplemental external beam radiotherapy and/or androgen deprivation therapy (ADT). METHODS: From April 1995 through February 2001, 686 consecutive patients underwent brachytherapy using either palladium-103 or iodine-125 for clinical Stage T1b-T3aNxM0 (2002 American Joint Committee on Cancer) prostate cancer. No patient underwent seminal vesicle biopsy or pathologic lymph node staging. The median follow-up was 59.5 months. The evaluated BMI subgroups were less than 25, 25.0 to 29.9, 30.0 to 34.9, and 35 or more kg/m2. Biochemical progression-free survival was defined by a prostate-specific antigen (PSA) level of 0.4 ng/mL or less after a nadir. The clinical, treatment, and dosimetric parameters evaluated for biochemical progression-free survival included BMI, patient age, clinical T stage, Gleason score, preimplant PSA level, risk group, percentage of positive biopsies, isotope, use of supplemental external beam radiotherapy, use of ADT, prostate volume, planning volume, percentage of target volume receiving 100%, 150%, and 200% of the prescribed dose, minimal percentage of dose covering 90% of the target volume, tobacco use, and the presence of hypertension and diabetes. RESULTS: For the entire group, the actuarial 8-year biochemical progression-free survival rate was 95.8%, 95.6%, 94.1%, and 100% for patients in BMI categories less than 25, 25.0 to 29.9, 30.0 to 34.9, and 35 or more kg/m2, respectively. In hormone-naive and hormone-manipulated patients free of biochemical progression, the median post-treatment PSA level was less than 0.1 ng/mL. When integrated across risk groups and ADT use, BMI had no statistically significant impact on biochemical progression-free survival. At last follow-up, 5 patients (0.7%) had died of metastatic prostate cancer. In multivariate Cox regression analysis, pretreatment PSA level, Gleason score, clinical stage, percentage of positive biopsies, ADT use, and tobacco status, but not BMI, were statistically significant predictors of 8-year biochemical progression-free survival. CONCLUSIONS: Prostate brachytherapy results in a high probability of 8-year biochemical progression-free survival for low, intermediate, and high-risk patients. When integrated across risk groups and hormonal status, BMI had no statistically significant influence on biochemical progression-free survival.