Transperineal 3D fusion imaging-guided targeted microwaves ablation for low to intermediate-risk prostate cancer: results of a phase I-II study.

Background: Targeted microwave ablation (TMA) is a novel modality of focal therapy to treat localized prostate cancer (PCa). We evaluated its short-term functional and oncologic outcomes.

Method: We performed a single-center, prospective, interventional phase I-II pilot trial (NCT04627896). TMA was performed in 11 patients with a single intracapsular MRI-visible lesion ≤12 mm, International Society of Urological Pathology (ISUP) grade ≤ 2, Prostate Specific Antigen (PSA) < 20 ng/mL, and a 5-mm safety distance from apex and rectum. Patients were treated with a 12 W very low-loss microwaves ablation system, guided by 3D ultrasound/MRI fusion imaging. Follow-up consisted in clinical visits, PSA and validated questionnaires. MRI was scheduled at five months and rebiopsy at six months. The primary endpoints of study were safety and efficacy (absence of tumour in the treated area).

Results: No severe complications were reported. All patients were discharged the same day of treatment without bladder catheter. No significant changes in PSA or questionnaires scores were reported. At rebiopsy, no cancer was found in five patients (45%); eight patients (73%) had an absence of in-field PCa and nine patients (82%) had an absence of in-field ISUP ≥ 2 PCa. New cancer foci outside the treated area were found in three patients (27%). Limitations of this study were the very limited sample size, the short follow-up, and the lack of a comparator.

Conclusions: TMA guided by fusion imaging is a safe modality with good ablative efficacy.