Single-Fraction High-Dose-Rate Brachytherapy Using Real-Time Transrectal Ultrasound–Based Planning in Combination With External Beam Radiation Therapy for Prostate Cancer: Dosimetrics and Early Clinical Results

Abstract

To validate the feasibility of a single-fraction High Dose Rate Brachytherapy (HDRBT) Boost for prostate cancer using real-time Transrectal Ultrasound (TRUS) based planning From August 2012 to September 2015, 126 patients underwent a single-fraction HDRBT boost of 15 Gy using real-time TRUS based planning. External beam radiation therapy (EBRT) (37.5 Gy/15f or 44Gy/22f or 45Gy/25f) was performed before (31%) or after (69%) HDRBT boost. Genito-Urinary (GU) and Gastro-Intestinal (GI) toxicity were assessed 4 and 12 months after the end of combined treatment using the International Prostate Symptom Score Scale (IPSS) and the Common Terminology Criteria for Adverse Events (CTCAE) v3.0. All dose-planning objectives were achieved in 90% of patients. Prostate D90 ≥105% and ≤ 115% was achieved in 99% of patients, prostate V150 ≤ 40% in 99%, prostate V200 < 11% in 96%, urethra D10 <120% for 99%, urethra V125 = 0% in 100% and rectal V75<1cc in 93% of patients. Median IPSS score was 4 at baseline and did not change at 4 and 12 months after combined treatment. No patients developed ≥ grade 2 GI toxicity. With a median follow-up of 10 months, only two patients experienced biochemical failure. Among patients who didn’t receive ADT, cumulative percentage of patients with PSA ≤ 1 ng/mL at 4 and 18 months was respectively 23% and 66%. Single-fraction HDRBT boost of 15 Gy using real-time TRUS based planning achieves consistently high dosimetry quality. In combination with EBRT, toxicity outcomes appear promising. A longer follow-up is needed to assess long-term outcome and toxicities.