OBJECTIVE: To compare the biochemical response in patients with locally advanced prostate cancer treated with external beam radiation therapy alone or in combination with conformal brachytherapy boost. MATERIALS AND METHODS: From November 1997 to January 2000, 74 patients received 45 Gy of pelvic external irradiation and four were treated with high dose rate iridium-192 conformal boost implants of 4 Gy each (BT). These were compared with 29 other patients treated with 45 Gy of pelvic external irradiation followed by a 24 Gy of bilateral ARC boost (RT) from October 1996 to February 2000. Some patients received neoadjuvant androgen deprivation therapy. Three-year actuarial biochemical control rates (BC3) and pretreatment biochemical response predictors such as prostate-specific antigen pretreatment (PSAi), Gleason score (GS) and clinical stage (CS), were evaluated. RESULTS: Median follow-up was of 25 months for the RT group and 37 months for the BT group. BC3 was 51% versus 73% (p = 0.032) for RT and BT, respectively. Comparisons of biochemical control by treatment group stratified by PSAi showed that BC3 for RT versus BT was 85.7% versus 79.1% (p = 0.76) for PSAi < 10 ng/mL and 38% versus 68% (p = 0.023) for PSAi > 10 ng/mL, respectively. For patients with GS < 6, BC3 was 37% versus 80% (p = 0.001) for RT versus BT and, for patients with GS > 6, BC3 was 78% versus 55% (p = 0.58) for RT versus BT, respectively. For patients with CS < T2a, BC3 was 36% versus 74% (p = 0.018) for RT versus BT and, for patients with CS > T2a, BC3 was 73% versus 69% (p = 0.692) for RT versus BT, respectively. The relative risk of biochemical relapse was 2.3 (95% IC: 1.0-5.1) for patients in RT group compared to the BT group. When adjusted for PSAi and GS, the relative risk of biochemical relapse was 2.4 (95% IC: 1.0-5.7). CONCLUSION: The treatment modality was an independent prognostic factor for biochemical relapse, with a significant improvement in the biochemical control with BT. These early results suggest that this treatment was most beneficial in patients with PSAi > 10 ng/mL, CS < T2a and GS < 6.
Prostate cancer; Radiotherapy; High dose rate brachytherapy
