Long-Term Prostate Cancer Control Using Palladium-103 Brachytherapy and External Beam Radiotherapy in Patients with a High Likelihood of Extracapsular Cancer Extension

Abstract

To report the long-term biochemical control rates with brachytherapy-based treatment for patients with prostate cancer at high risk of extracapsular cancer extension. A total of 243 consecutive patients with at least one higher risk factor (Gleason score of 7 or worse, prostate-specific antigen [PSA] level greater than 10 ng/mL, or elevated prostatic acid phosphatase level greater than 2.5 U) who were treated with palladium-103 plus supplemental external beam radiotherapy from 1992 through 1996 were included in this study. Patients received 41 Gy external beam radiotherapy to a limited pelvic field, followed 4 weeks later by a palladium-103 boost. The prescribed minimal palladium-103 dose to the prostate was 80 to 90 Gy. Freedom from biochemical failure was defined as a serum PSA level of 0.2 ng/mL or less at the last follow-up visit. Of the 243 patients, 41 developed biochemical failure. The overall actuarial freedom from biochemical progression rate at 13 years was 81%, with 198 patients followed up for longer than 5 years. The overall actuarial freedom from failure rate for the 93 patients with a PSA level of 10 ng/mL or greater and Gleason score of 7 or greater was 74% at 5 years and 72% at 10 years. The overall actuarial freedom from failure rate for the 66 patients with elevated prostatic acid phosphatase was 65% at 10 years. The absolute risk of failure decreased progressively with time, falling to 1% by 6 years after treatment. On Cox proportional hazard multivariate analysis, considering each factor as a continuous variable, the strongest predictor of failure was the acid phosphatase level (P <0.0001), followed by Gleason score (P = 0.42) and PSA level (P = 0.15). The evidence from this patient group at high risk of extracapsular cancer extension suggests that the relatively high tumor control rates with brachytherapy-based therapy are durable.