21 Gy Single Fraction Prostate HDR Brachytherapy: Mature Results of a Single Institution Prospective Study
Conference Proceeding - Restricted Access
PurposeTo present the outcome and toxicity results of a prospective trial of 21 Gy single fraction high-dose-rate (HDR) brachytherapy for men with low- or intermediate-risk prostate cancer.
Materials and MethodsPatients were treated according to an IRB-approved prospective study of single fraction HDR brachytherapy. All patients had low- or intermediate-risk prostate cancer with tumor stage ≤ T2b, PSA ≤ 15, and Gleason score ≤ 7. Patients with prostate volumes > 50 cc or <12 cc, taking alpha-blockers for urinary symptoms, or with baseline American Urologic Association (AUA) symptom scores > 12 were ineligible. Patients underwent trans-rectal ultrasound (TRUS)-guided trans-perineal implant of the prostate followed by single fraction HDR brachytherapy. Treatment was delivered via Ir-192 to a dose of 21 Gy, prescribed to the prostate with no additional margin applied. Treatment planning was TRUS-based with constraints as follows: prostate V100 > 95%; urethral V115 < 1%; rectal V72 ≤ 1% prescription dose.
ResultsA total of 26 patients were enrolled. Median follow up was 4.0 years (range 0.6-5.7 years). Median age was 64 years. Median gland volume at the time of treatment was 41 cc. 88.5% of patients had T1 disease, 15.4% had Gleason score 6, 84.6% Gleason score 7, and median pre-treatment PSA was 5.0 (range 2.7-12.2) ng/mL. Acute and chronic grade 2 GU toxicity rates were 26.9% and 38.5%, respectively. Acute grade 3 GU toxicity rate was 11.5%. There were no chronic grade 3 GU toxicities. There were no grade 2+ acute or chronic GI toxicities. The 5-year biochemical failure rate was 35.1%. The 5-year radiographic local failure rate was 32.4%. Biopsy-proven local failure at 5-years was 15.3%. Two patients underwent salvage treatment after experiencing radiographic local failure, without an attempted biopsy of the prostate. No patients developed biopsy proven or radiographic regional lymph node recurrence or distant metastasis. 5-year overall survival was 96.2%. The single patient death was a result of a myocardial infarction approximately 7 months after protocol treatment. Cause-specific survival at 5 years was 100%.
ConclusionsDespite being well-tolerated, 21 Gy single fraction HDR brachytherapy is associated with high biochemical and local failure rates. The results from this prospective pilot study do not support continued investigation of this dosing regimen in subsequent investigation.
Salari K, Ye H, Sebastian E, Limbacher A, Johnson M, Mitchell B, et al. [Thompson A, Seymour Z, Nandalur S, Krauss D]. 21 Gy single fraction prostate HDR brachytherapy: mature results of a single institution prospective study. Brachytherapy. 2022 Nov-Dec;21(6 Suppl):S22. doi:10.1016/j.brachy.2022.09.017.
American Brachytherapy Society Annual Conference, June 17-19, 2022, Denver, CO.