Unfavorable Intermediate- and High-Risk Prostate Cancer Treated With Predominantly Brachytherapy Alone With Long-Term Follow-Up

Abstract

Abstract Objective: Assess 10-year outcomes of brachytherapy (BT) with or without supplemental external-beam radiation therapy (S-EBRT) for treatment of unfavorable intermediate-risk prostate cancer (U-IRPC) and high-risk prostate cancer (HRPC). Materials and Methods: Retrospective analysis using multivariable analysis (MVA) and propensity score matching was performed on 156 patients with U-IRPC and HRPC between 2004 and 2016. Favorable HRPC was defined as T1c-T2c, Gleason group 4, and prostate-specific antigen (PSA) < 10.0. In total, 129 patients underwent BT alone using iodine-125 to 145 Gy, while 27 underwent S-EBRT + BT boost to 110 Gy. S-EBRT dose was 45-46 in 1.8-2.0 Gy fractions to the prostate and seminal vesicles. Freedom from biochemical failure (FFBF) was defined by the Phoenix definition of PSA failure. Complications were assessed using the Radiation Therapy Oncology Group grading scale. Results: Median follow-up was 8.2 vs 8.3 years for BT vs S-EBRT + BT. FFBF for U-IRPC vs HRPC was 80.7% vs 55.6% (P < .01), and metastases-free survival (MFS) was 94.5% vs 72.6% (P < .01). The S-EBRT + BT group had higher Gleason group (P = .01) and higher percent positive biopsy cores >50% (P < .01), but also higher use of neoadjuvant androgen deprivation therapy, P < 0.01. On MVA, higher clinical stage (P < .01) and Gleason group (P = .04) independently predicted a lower MFS, whereas higher Charlson score predicted lower overall survival, P = 0.01. The adjusted 10-year FFBF and MFS for BT alone vs S-EBRT + BT were 76.8% vs 72.9% (P = .70) and 90.8% vs 87.3% (P = .81). Favorable HRPC had a 10-year FFBF of 91.7% vs unfavorable HRPC of 31.7%, P < 0.01. Prevalence of urinary (P = .04) and rectal (P < .01) complications was higher using S-EBRT, although this was mostly in grades 1 and 2. Conclusion: Low-dose-rate BT using iodine-125 alone is a reasonable treatment option for U-IRPC and favorable HRPC, which is effective, convenient, and cost-effective.