Targeted microwave ablation of localised prostate cancer (VIOLETTE trial): a prospective multicentre study

To assess the oncological outcomes of targeted microwave ablation (TMA) using organ-based tracking (OBT) Fusion® via KOELIS Trinity® (KOELIS, Meylan, France) in men with intermediate-risk prostate cancer (PCa): the VIOLETTE trial (ClinicalTrials.gov identifier: NCT04582656) PATIENTS AND METHOD: In this prospective phase II, multicentre European study, men with a prostate-specific antigen (PSA) level <20 ng/mL, a single magnetic resonance imaging (MRI)-visible lesion ≤15 mm, International Society of Urological Pathology (ISUP) Grade Group 2 on MRI-targeted biopsy, and clinical T stage ≤2, were enrolled. The microwave applicator was placed using OBT Fusion guidance, either transperineally or transrectally. The primary endpoint was the absence of clinically significant PCa (csPCa), defined as ISUP Grade Group ≥2, within the treated area at 12 months. Secondary endpoints included safety, functional outcomes using validated measures, and the need for subsequent radical treatment.

A total of 76 patients were treated across six centres with 66 (87%) completing the 12-month follow-up. At 6 months, six patients had csPCa after positive MRI control, including four within the treated area. At 12 months, csPCa was detected in 15 additional patients, including nine in-field recurrences, yielding an 81% in-field csPCa-free rate. Five serious adverse events in three patients were reported. Sexual (-2.5 points; P < 0.001) and ejaculatory (-1 points; P < 0.001) scores decreased significantly, whereas urinary function remained stable. Radical treatment was required in four (5.2%) patients at 12 months.

Targeted microwave ablation using OBT Fusion technology appears to be a safe and effective focal therapy procedure for localised intermediate-risk PCa. The VIOLETTE trial achieved its primary endpoint, with 81% patients free of in-field csPCa at 12 months.