Results of high-dose rate iridium-192 brachytherapy boost to external beam radiation therapy for prostate cancer in Japanese men

Abstract

4776 Background: Afterloading brachytherapy is the sole modality of interstitial radiotherapy currently available in Japan for treating prostate cancer. This technique has several advantages over permanent seed implantation, including absence of radiation protection and safety issues for patient. Also dosimetry can be based on images with the needles in situ, making it easy to optimize the dose. Currently several clinical trials reported that HDR brachytherapy is also appropriate for high risk (unfavorable) prostate cancer. To aim of this study is to evaluate treatment outcome of HDR brachytherapy and EBRT combined with or without neoadjuvant/adjuvant androgen ablation for patients with prostate cancer. Methods: From June 1999 to April 2003, 108 patients with clinically localized or locally extensive prostate carcinoma (T1N0M0-T3N0M0) were treated with HDR iridium-192 brachytherapy followed by 30 Gy EBRT. The whole prostate and any tumor extension beyond the capsule were irradiated five times over 3 days using an HDR Ir-192 source with a nominal activity of 370 GBq and each single dose was 7.5 Gy. Three days after HDR fraction, 3D conformal radiation was given using a fractionation of five times 3.0 Gy per week, specified at the isocenter, for 2 weeks. After June 2000, patients in the high risk group were given 6 months’ of neoadjuvant endocrine therapy followed by 36 months’ of adjuvant endocrine therapy following radiation therapy. The recommendations of the consensus panel of the ASTRO were followed for assessing biochemical failure. Results: The median age of the 108 patients was 70.5 years (range 50–84 years). Low risk patient was found in 20, intermediate risk in 30 and high risk in 58 patients, with a median follow-up was 31.5 months (range: 12–58months). The overall actuarial biochemical control rate (bNED) was 81.5%. The bNED in 36 months for low risk, intermediate risk, and high risk patient was 95.0%, 77.4% and 74.7%, respectively. Conclusions: HDR brachytherapy and EBRT combined with or without neoadjuvant/adjuvant androgen ablation is an effective treatment modality for prostate cancer and encouraging biochemical control rates after a median follow-up of 31.5 months. No significant financial relationships to disclose.