A Randomized Comparison of High-Dose-Rate and Low-Dose-Rate Prostate Brachytherapy Combined With External Beam Radiation Therapy for Unfavorable Prostate Cancer: Efficacy Results After Median Follow-up of 74 Months.

Abstract

This single-center randomized trial compared health-related Quality of Life for men with unfavorable localized prostate cancer treated with combined pelvic external beam radiation therapy (EBRT) and prostate brachytherapy, randomly assigned to high-dose rate (HDR) or low-dose rate (LDR). We now report efficacy outcomes with a minimum 5-year follow-up. Consenting patients receiving pelvic EBRT combined with prostate brachytherapy were randomized to either LDR (110 Gy) or HDR (15 Gy). Androgen deprivation was used in 76% of patients. EBRT delivered 46 Gy/23 using intensity modulated radiation therapy or volumetric-modulated arc therapy (68%) or 3-dimensional conformal radiotherapy (32%). Follow-up up was 1, 3, and 6 months, then every 6 months to 3 years, and then annually. Prostate-specific antigen (PSA) ≤0.2 ng/mL at 4 years defined cure. Biochemical failure-free survival (bFFS) and overall survival were calculated by Kaplan-Meier methods. All failures were investigated by imaging (computed tomography, bone scan, and/or Prostate Specific Membrane Antigen- Positron Emission Tomography (PET) ± biopsy if PET was not available. From January 2014 to December 2019, 195 men (42% intermediate risk/58% high risk) were randomly assigned: 108 to HDR and 87 to LDR. The median age was 71 years. Median PSA was 11.6 ng/mL (mean, 27.0 ng/mL). Median follow-up was 74 months (43-116 m). The median PSA nadirs were 0.07 and 0.08 in HDR and LDR (P = .16), and time to nadir was 13.8 and 14.1 months, respectively (P = .87). Four-year PSA ≤0.2 was maintained in 81% and 83% of HDR and LDR (P = .91). Eight-year bPFS (nadir + 2) was 86% and 85%, respectively. Eighteen of 22 biochemical failures have been identified; 3 are isolated local failures, whereas 14 are distant failures (isolated 11; 3 combined). In this small, randomized comparison, efficacy analysis shows no difference between LDR and HDR boost in bPFS at 5 and 8 years and confirms the excellent efficacy of dose escalation using prostate brachytherapy as documented in Ascende-RT for unfavorable localized prostate cancer.