High-dose-rate brachytherapy and hypofractionated external beam radiotherapy combined with long-term androgen deprivation therapy for very high-risk prostate cancer

Objective To estimate the outcomes of high-dose-rate brachytherapy combined with hypofractionated external beam radiotherapy in prostate cancer patients classified as very high risk by the National Comprehensive Cancer Network. Methods Between June 2009 and September 2015, 66 patients meeting the criteria for very high-risk disease received high-dose-rate brachytherapy (2 fractions of 9 Gy) as a boost of external beam radiotherapy (13 fractions of 3 Gy). Androgen deprivation therapy was administered for approximately 3 years. Biochemical failure was assessed using the Phoenix definition. Results The median follow-up period was 53 months from the completion of radiotherapy. The 5-year biochemical failure-free, distant metastasis-free, prostate cancer-specific and overall survival rates were 88.7, 89.2, 98.5 and 97.0%, respectively. The independent contribution of each component of the very high-risk criteria was assessed in multivariable models. Primary Gleason pattern 5 was associated with increased risks of biochemical failure (P = 0.017) and distant metastasis (P = 0.049), whereas clinical stage >= T3b or >4 biopsy cores with Gleason score 8-10 had no significant impact on the two outcomes. Grade 3 genitourinary toxicities were observed in two (3.0%) patients, whereas no grade >= 3 gastrointestinal toxicities occurred. Conclusions The present study shows that this multimodal approach provides potentially excellent cancer control and acceptable associated morbidity for very high-risk disease. Patients with primary Gleason pattern 5 are at a higher risk of poor outcomes, indicating the need for more aggressive approaches in these cases.