Comparison Of Long-Term Outcomes For Patients With High-Risk Prostate Cancer Treated With Ebrt Alone Versus Combination Ebrt With A Ldr Brachytherapy Boost

To compare the long term outcomes for patients with high-risk prostate cancer treated with external beam radiation therapy (EBRT) versus those treated with combined EBRT with a Low-Dose-Rate (LDR) brachytherapy boost. Patients treated for high-risk localized prostate cancer at a single institution between 1997 and 2013 were retrospectively identified. A total of 121 patients were treated with combination therapy over this time. A total of 71 EBRT alone patients were identified; due to limitations in the electronic medical records, detailed records for patients treated with EBRT alone from 1997-2003 were unavailable for immediate review (in the process of being retrieved from archives and full results will be presented). Combination therapy patients were treated with EBRT followed by Pd-103 implants to a prescription dose of 90-100 Gy. Clinical and treatment-related data were recorded, including: age, stage, treatment parameters, toxicity, and outcomes. Toxicities were graded using the Common Terminology Criteria for Adverse Events (CTCAE). Kaplan Meier (KM) curves were generated to estimate overall survival (OS), biochemical failure free survival (b-PFS), and distant metastasis free survival (DMFS). Median follow up for the combination therapy cohort was 134 months and median age was 65 years. Median follow up for the EBRT cohort was 56 months and median age was 70 years old. The median ADT duration was 6 months and the interquartile range (IQR) was 3.25-8 months for the combination therapy group versus a median of 8 months and an IQR of 5-23 months for the EBRT group. The 5- and 10-year KM b-PFS estimates were 86.1% and 77.4% for the combination cohort versus 80.2% and 57% for the EBRT cohort (p=0.221 and p=0.05). The 5 and 10 year KM DMFS estimates were 94.8% and 88.9% for the combination cohort versus 93.8% and 71.8% for the EBRT cohort (p=0.440 and p=0.173). The median time to biochemical failure was 48 months in the combination group versus 35 months in the EBRT group. The median time to distant metastases was 57 months in the combination cohort versus 54 months in the EBRT cohort. Less than 5% of patients treated with combination therapy (n=5) experienced late grade 3 GU toxicity. The 5 and 10 year KM OS estimates were 88.3% and 74.9% for the combination cohort versus 73.2% and 49.6% for the EBRT cohort. Despite, the shorter follow up time and use of longer-term ADT in the EBRT alone cohort, there was still a statistically significant difference in in b-PFS at 10 years, and trend toward improved DMFS, in favor of combination therapy. While the follow up differed between the two groups, the median follow up for the combination therapy cohort was almost twice as long as that in the primary report of the ASCENDE-RT trial. Updated analysis, including more patients with longer follow up for the EBRT cohort will be presented at ASTRO.