Abstract
INTRODUCTION AND OBJECTIVE: Padeliporfin (WST11) vascular-targeted photodynamic therapy (VTP) has shown significant clinical benefit as a localized partial gland ablation (PGA) therapy when compared to active surveillance for low-risk prostate cancer, by curbing progression and the need for radical treatment, leading to its regulatory approval in Europe. This Phase 2b trial prospectively investigated WST11-VTP for intermediate-risk cancers. METHODS: 50 men with unilateral Grade Group 2 (GG2) cancers (Gleason 3+4) evaluated with MRI and ultrasound-guided (TRUS) biopsy were treated with up to 2 sessions of unilateral PGA using padeliporfin VTP. Eligibility criteria included <cT2b, PSA <10, and fusion biopsy for PIRADS 3+ lesions on pretreatment MRI. Contralateral very lowerisk disease was observed. MRI and systematic, 14-core TRUS biopsy (+/- fusion) were performed 3 and 12 months after treatment, evaluating for Gleason Grade 4 or 5 (≥GG2) cancer as the primary endpoint. Additional data included adverse events and patient-reported quality of life. The study was powered using β=0.2 to reject the null hypothesis (r≥70%), using a one-sided exact binomial test with 5% alpha risk. To be valid, 44 evaluable patients were required by the 12-month primary endpoint. Treatment safety and patient-reported quality of life for sexual and urinary function were assessed with validated questionnaires (IIEF-15 and IPSS, respectively). RESULTS: 46 men were evaluable for the 12-month primary endpoint. Before 12 months, 1 man proceeded to prostatectomy (treatment failure), 2 men refused 12-month biopsy, and 1 man died of COVID-19. 12/49 (24%) underwent per-protocol second hemiablation treatment for GG2 tumor at 3 months: 9 for residual cancer and 4 with newly identified contralateral GG2 tumors (1 bilateral). 45 of the 46 evaluable men underwent 12-month biopsy: 38 (83%) had no Gleason grade 4 or 5 cancer, including 11/12 (92%) patients receiving 2 treatments. By 3 months, median decline in IIEF-5 score from baseline was -1.0 (IQR -7,0). Median improvement in IPSS score was -1.0 (IQR -1,5), with pad-free continence observed in 100% of patients. Median change in IIEF score by 12-months was -1.0 (IQR -5,0). Grade 3 treatment-related adverse events occurred in 6 (12%) patients;all procedure-related prostate/pelvic pain resolved by 3 weeks. CONCLUSIONS: These positive trial results show that WST11- VTP is effective for PGA of intermediate-risk prostate cancer with minimal toxicity including impact on urinary and sexual function, consistent with the Phase 3 trial results in low-risk disease. Based on these data this therapy bears consideration for approval as a conservative therapeutic option for selected cases of intermediate risk disease.
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