International Journal of Radiation Oncology Biology Physics
International Journal of Radiation Oncology Biology Physics
5 years ago

IDEAL 2a phase-II study of ultra-focal brachytherapy for low and intermediate risk prostate cancer

Focal therapy of prostate cancer requires precise positioning of therapeutic agents within well-characterised index tumours (IT). We assessed the feasibility of low-dose-rate ultra-focal brachytherapy (UFB). Methods & Materials IRB-approved European Clinical Trials Database-registered phase II protocol. Patients referred (10/2013-8/2016) for active surveillance [PSA<10ng/mL, cT1c-cT2a, Gleason sum on referring biopsies ≤6(3+3), ≤3 positive biopsies, ≤50% of cancer] were pre-selected. Inclusion was confirmed when complementary image-guided biopsies informed a single PI-RADS.v1≥3 Gleason sum ≤7a(3+4) lesion. A single ultrasound-visible ancillary marker was positioned within the IT using 3D-TRUS/MRI elastic fusion registration (Koelis°). Ultra-focal transperineal delivery of I-125 seeds then used classical 2D-Transrectal ultrasonography (Bard-FlexFocus°) and dose-optimization (Variseed Treatment Planning System°). Following Simon's optimal design, 17 patients were required to assess the feasibility of delivering ≥95% of the prescribed dose (160Gy) to the IT (primary objective). Adverse-events (CTCAE) and quality-of-life (IIEF-5, IPSS) were recorded. 1-year control biopsies were obtained in IT and untreated segments. Results 27/44 of pre-selected patients failed inclusion. 16/17 of UFB-treated patients met the primary objective (per-protocol success). Prescription dose was delivered to 14.5±6.4% of the prostate volume resulting in negligible urethral and rectal irradiations and toxicities. No recurrences were evidenced on 1-year control MRI and IT biopsies. Seven non-clinically significant cancers and one Gleason sum 7a(3+4) cancer (salvage prostatectomy) were observed in the untreated parenchyma. Conclusions Recent technology allows selective and effective brachytherapy of small MRI targets.

Publisher URL: www.sciencedirect.com/science

DOI: S0360301618301809

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