Single-fraction brachytherapy as monotherapy for early-stage prostate cancer: The UCSF experience.

Abstract

PURPOSE\nHigh-dose-rate (HDR) brachytherapy as monotherapy is an effective treatment option for localized prostate cancer, but experience with single-fraction brachytherapy is limited by studies with small sample size. We report a large single-institution experience with single-fraction HDR brachytherapy as monotherapy for early-stage prostate cancer.\n\n\nMETHODS AND MATERIALS\nRetrospective chart review was performed for men treated with HDR brachytherapy as monotherapy for low- to intermediate-risk prostate cancer. Competing risk analyses were performed to estimate subdistribution hazard ratio and cumulative incidence of biochemical recurrence (BCR) and prostate cancer-specific mortality.\n\n\nRESULTS\nWe identified 124 men with a median followup of 2.2\xa0years (interquartile range 25th to 75th percentile: 1.8-3). Overall, 21.0% of patients (n\xa0= 26) were low risk, 44.4% (n\xa0= 55) were favorable intermediate risk, and 34.7% (n\xa0= 43) were unfavorable intermediate risk. At 2\xa0years, the cumulative incidence of BCR was 3.5%: 0% for low risk, 4.0% for favorable intermediate risk patients, and 4.5% for unfavorable intermediate risk patients. In total, 12 BCRs were observed (9.7%) and approximately half occurred after median followup of 2.2\xa0years. Compared with low-risk and favorable intermediate-risk disease, unfavorable intermediate-risk disease was significantly associated with BCR (subdistribution hazard ratio: 3.6, 95% CI: 1.1 to 11.1, p\xa0= 0.03). Prostate cancer-specific mortality was 0%. No patient experienced Grade 3 or higher acute or late genitourinary toxicity.\n\n\nCONCLUSIONS\nSingle-fraction brachytherapy for early-stage prostate cancer was safe with promising short-term disease control rates, especially for low-risk patients. Longer term followup is needed as we observed an overall BCR rate of 9.7%.