A Prospective Phase II Trial of Trans-perineal Ultrasound-Guided Brachytherapy for Locally Recurrent Prostate Cancer after External Beam Radiotherapy (NRG Oncology/RTOG -0526)
Mené sur 92 patients atteints d'un cancer de la prostate (âge médian : 70 ans ; durée médiane de suivi : 54 mois), cet essai multicentrique de phase II évalue la toxicité à long terme (9 à 24 mois après le traitement) de grade supérieur ou égal à trois d'une curiethérapie de sauvetage à faible débit de dose
Purpose : Only retrospective data is available for low dose rate (LDR) salvage prostate brachytherapy for local recurrence after external beam radiotherapy (EBRT). The primary objective of this prospective Phase II trial (NCT00450411) was to evaluate late gastrointestinal and genitourinary adverse events (AEs) after salvage LDR brachytherapy. Materials/Methods : Eligible patients had low/intermediate risk prostate cancer prior to EBRT and biopsy-proven recurrence >30 months after EBRT, with PSA <10 ng/mL and no regional/distant disease. The primary endpoint was grade 3 or higher late treatment-related GI/GU AEs occurring 9-24 months after brachytherapy. These were projected to be <10%, with >20% considered unacceptable. All events were graded with CTCAE V3.0. Multivariate analyses investigated associations of pre-treatment or treatment variables with AEs. Results : From May 2007 to January 2014, 100 patients were registered from 20 centers. 92 analyzable patients had a median follow-up of 54 months (range: 4-97) and median age 70 (IQR: 65-74). Initial Gleason score was 7 in 48%. Median dose of EBRT was 74 Gy (IQR: 70-76) at a median interval of 85 months previously (IQR: 60-119). Only 16% had androgen deprivation at study entry. Twelve patients (14%) had late grade 3 GI/GU AEs with no treatment-related grade 4 or 5 AEs. No pre-treatment variable predicted late AEs, including prior EBRT dose and elapsed interval. Higher V100 (% of prostate enclosed by prescription isodose) predicted both occurrence of late AEs (OR=1.24; 95% CI: 1.02-1.52; p=0.03) and earlier time to first occurrence (HR=1.18; 95% CI: 1.03-1.34; p=0.02). Conclusions : This prospective multicenter trial reports outcomes of salvage LDR brachytherapy for post EBRT recurrence. The rate of late grade 3 AEs did not exceed the unacceptable threshold. The only factor predictive of late AEs was implant dosimetry reflected by V100. Efficacy outcomes will be reported at a minimum of 5-yr follow-up.