Presentation Authors: Takashi Kasahara*, Kazutoshi Yamana, Ryo Maruyama, Motoki Kaidu, Hidefumi Aoyama, Niigata, Japan, Tsutomu Nishiyama, Uonuma, Japan, Yoshihiko Tomita, Niigata, Japan
Introduction: Since 2014 version, the National Comprehensive Cancer Network (NCCN) guidelines for prostate cancer (PCa) have further subdivided high-risk group to separate patients thought to have the worst prognosis into the very high-risk (VHR) category. The revised criteria for VHR include clinical stage â‰¥ T3b or primary Gleason 5 or â‰¥ 5 biopsy cores with Gleason 8-10. High-dose-rate brachytherapy (HDRBT) allows dose escalation while minimizing acute or late toxicity, and has been widely applied especially in high risk or locally advanced PCa. However, there remains little clear evidence of benefit of this treatment modality in VHR subpopulation. The purpose of this study was to report the outcomes of HDRBT and hypofractionated external beam radiotherapy (EBRT) combined with long-term androgen deprivation therapy (ADT) for VHR PCa.
Methods: Between June 2009 and September 2015, all patients who had undergone HDRBT for nonmetastatic PCa at our institution were retrospectively identified. Of these, 66 patients meeting NCCN criteria for VHR disease were included in this study. HDRBT with 2 fractions of 9 Gy was administered after completion of EBRT with 13 fractions of 3 Gy each. All patients initially underwent â‰¥ 6 months of neoadjuvant ADT, and adjuvant ADT was continued for 36 months after HDRBT. Biochemical failure (BCF) was assessed using the Phoenix definition.
Results: The median (interquartile range) follow-up was 53 (41-70) months from the start of radiotherapy. The 5-year BCF-free, metastasis-free, disease-specific, and overall survival rates were 88.7%, 89.2%, 98.5%, and 97.0%, respectively. The independent contributions of each component of the VHR criteria were assessed in multivariable models. Primary Gleason 5 was associated with increased risks of BCF (HR = 13.77; 95% CI, 1.61-118.05, P = 0.017) and metastasis (HR = 5.51; 95% CI, 1.01-30.08, P = 0.049) whereas clinical stage â‰¥ T3b or â‰¥ 5 biopsy cores with Gleason 8-10 had no significant impact on the two outcomes.Grade 3 genitourinary toxicities were observed in 2 (3.0%) patients (hematuria and urethral stricture), all of which were successfully controlled by endoscopic interventions. Neither acute nor late â‰¥ Grade 3 gastrointestinal toxicity was seen.
Conclusions: Although a longer follow-up is needed to confirm the durability of these findings, the present study indicates that this multimodal approach provides potentially excellent cancer control and acceptable associated morbidity for VHR PCa. Patients with primary Gleason 5 were at a higher risk of poor outcome, indicating a need for more aggressive approaches in these patients.