The addition of a brachytherapy (BT) boost to external beam radiotherapy (EBRT) reduces recurrence risk in men with high-risk prostate cancer (PCa) and may reduce PCa-mortality for Gleason grade group 5 (GG5). Whether the extent of pattern five, a risk factor for distant metastases, impacts the benefit of a BT boost is unclear.
Men with localized GG5 PCa treated with (1) EBRT or (2) EBRT+BT between 2010 and 2016 were identified in the National Cancer Database. EBRT monotherapy group received conventionally fractionated (1.8-2.0 Gy per fraction) ≥74 Gy or moderately hypofractionated (2.5-3.0 Gy per fraction) ≥60 Gy. EBRT + BT group received conventionally fractionated ≥45 Gy or moderately hypofractionated ≥37.5 Gy, and either LDR or HDR BT. All patients received concomitant ADT; none received chemotherapy, immunotherapy, or surgery. OS was compared using Kaplan-Meier, log-rank test, and multivariable Cox proportional hazards in the overall cohort, followed by subgroups based on primary versus secondary pattern 5. Propensity score- and exact-matching was used to corroborate results.
A total of 8260 men were eligible: EBRT alone (89%) versus EBRT + BT (11%). 5-year OS for EBRT versus EBRT + BT was 76.3% and 85.0%, respectively (p = 0.002; multivariable adjusted HR 0.84, 95% CI 0.65-0.98; p = 0.04). These results remained consistent after propensity score and exact matching. The OS advantage of a BT boost was more prominent in men with Gleason 4 + 5 PCa (p = 0.001) and not observed in men with Gleason 5 + 5 or 5 + 4 PCa.
Extent of pattern five may be useful in appropriately selecting men for EBRT+BT and should be considered as a pre-randomization stratification variable for future clinical trial design.
Brachytherapy. 2023 Jan 10 [Epub ahead of print]
Sagar A Patel, Brian Baumann, Jeff Michalski, Randall Brenneman, Bill Zheng, Hiram Gay, Daniel Ferraro, Simon A Brown, Albert J Chang, Peter J Rossi, Benjamin W Fischer-Valuck
Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, GA. Electronic address: ., Department of Radiation Oncology, Washington University, St. Louis, MO., Department of Radiation Oncology, Winship Cancer Institute, Emory University, Atlanta, GA., Springfield Clinic, Springfield, IL., Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA., Calaway Young Cancer Center, Valley View Hospital, Glenwood Springs, CO.