71 Background: The purpose of this study was to compare clinical outcomes in a cohort of intermediate- and high-risk prostate cancer patients treated with either dose-escalated adaptive IGRT or pelvic external beam RT with high-dose rate brachytherapy boost (EBRT+HDR). Methods: 1,520 patients with clinical stage T1-T3 N0 M0 prostate cancer were treated with either CT-based offline adaptive IGRT (n=1,037) or EBRT+HDR, n=438) at William Beaumont Hospital. For IGRT, the CTV included the prostate and proximal seminal vesicles only. Median dose (minimum to cl-PTV) delivered via 3D conformal RT or intensity-modulated RT was 75.6 Gy (range: 73.8-79.2 Gy). For EBRT+HDR, the whole pelvis was treated to 46 Gy + 2 HDR implants with a median of 10.5 Gy (8.75-11.5 Gy) per implant. 208 patients from each group were matched based on criteria of pretreatment PSA ± 4 ng/mL, same Gleason score, T stage ± 2 sublevels, and use of neoadjuvant androgen deprivation therapy (ADT). Results: Mean follow-up was 5.1 years for IGRT vs 7.0 years for EBRT+HDR. Mean pretreatment PSA was 9 for both groups. Mean Gleason was 7 for both groups. EBRT+HDR patients were younger (67 vs 71 years, p<0.01) with a higher percentage of positive biopsy cores (51% vs 39%, p<0.01). Intermediate risk patients comprised 78% and 76% for IGRT and EBRT+HDR, respectively (p=0.56). 42% in each treatment group received neoadjuvant or concurrent ADT. 5-year biochemical control (BC) based on the Phoenix definition was 91% for IGRT vs 87% for EBRT+HDR (p=0.60). For intermediate-risk, 5-year BC was 94% vs 87% (p=0.71) and was 86% vs 86% (p=0.83) for high-risk patients. No significant differences were noted between the 2 groups for local recurrence, distant metastasis, clinical failure, overall survival, and cause-specific survival. Conclusions: In this matched-pair analysis of 416 patients, treatment of intermediate and high-risk prostate cancer with either offline adaptive IGRT or EBRT+HDR yielded excellent clinical outcomes without significant differences. The omission of pelvic radiotherapy in the IGRT patients did not appear to be associated with poorer clinical outcomes with modern high-dose RT. No significant financial relationships to disclose.
A Dose-Escalation Study for High-Dose-Rate Brachytherapy Boost in Intermediate- and High-Risk Prostate Cancer Patients
