Intermediate-Risk Localized Prostate Cancer in the PSA Era: Radiotherapeutic Alternatives

Abstract

To retrospectively compare the biochemical disease-free survival (BDFS) of patients treated with standard dose external beam radiotherapy (SD-EBRT), SD-EBRT plus androgen deprivation (AD), and brachytherapy-based treatment (brachytherapy with or without EBRT with or without AD). All 297 patients with intermediate-risk prostate cancer treated with these radiation-based treatments at our institution from August 1989 to June 2001 were included. Biochemical relapse was defined according to the American Society for Therapeutic Radiology and Oncology (ASTRO) definition, a prostate-specific antigen level of 1.5 ng/mL or greater and rising on two consecutive occasions (the "Bolla" definition), and the current prostate-specific antigen nadir plus 2 ng/mL with failure dated "at call" (the "Houston/Phoenix" definition). The number of patients treated with SD-EBRT, SD-EBRT plus AD, and brachytherapy-based treatment was 141, 84, and 72, respectively. The year of treatment was analyzed as a prognostic factor. The median follow-up was 32.3, 34.7, and 41.5 months for the ASTRO, Bolla, and Houston/Phoenix definitions, respectively. The brachytherapy-based treatment resulted in improved BDFS compared with SD-EBRT (ASTRO definition, 5-year BDFS rate 88% +/- 5% versus 49% +/- 5%, P <0.01; Bolla definition, 88% +/- 8% versus 49% +/- 5%, P <0.01; Houston/Phoenix definition, 81% +/- 10% versus 64% +/- 5%, P = 0.01). SD-EBRT plus AD was superior to SD-EBRT alone using the Bolla definition (5-year BDFS 76% +/- 7% versus 49% +/- 5%, P <0.01) and the Houston/Phoenix definition (85% +/- 6% versus 64% +/- 5%, P = 0.01), but not using the ASTRO definition (P = 0.17). Multivariate analysis, including prostate-specific antigen, clinical stage, Gleason score, and year of treatment, demonstrated improved biochemical outcomes for brachytherapy-based treatment versus SD-EBRT (ASTRO, P <0.01; Bolla, P <0.01; and a trend toward significance with Houston/Phoenix, P = 0.07) and for the addition of AD to SD-EBRT (Bolla, P <0.01 and Houston/Phoenix, P = 0.03). The year of treatment trended toward significance (P = 0.077) on multivariate analysis using the ASTRO definition. For patients with intermediate-risk prostate cancer, brachytherapy-based treatment and the addition of AD to SD-EBRT resulted in improved biochemical outcomes compared with the outcomes with SD-EBRT alone; however, these findings were dependent on the definition of biochemical failure used. The year of treatment may be an important prognostic factor in intermediate-risk prostate cancer.