Optimizing prostate cancer treatment with MR-guided focused ultrasound: the role of expanded ablation-to-lesion volume ratio.

objectiveTo determine which treatment parameters optimize focal therapy for intermediate-risk prostate cancer by balancing oncologic control with healthy tissue preservation, in a phase 2b multicenter trial of MRI-guided Focused Ultrasound (MRgFUS). Additionally, to assess the relationship of ablation volume relative to lesion volume with oncologic outcomes, urinary, and erectile function. MATERIALS AND

methodsIn this retrospective interpretation of prospectively acquired data, the non-perfused volume (NPV) of prostate tissue encompassing the MRI-visible lesion volume defined the ablation-volume-to-lesion-volume ratio (ALVR). Oncologic efficacy was assessed as the absence of clinically significant (GGG ≥ 2) cancer in the treatment zone at 24-month biopsy. Associations between ALVR and outcomes were assessed using Student's t-tests. Baseline characteristics were compared using Kruskal-Wallis tests.

resultsEighty-nine men (mean age, 63 years ± 7) had MRI-visible lesions with a volume of 0.47 mL (IQR: 0.20-0.95), with a surrounding NPV of 6.9 mL (IQR: 5.2-10.4). Men achieving oncologic efficacy had twice the ALVR compared to those with recurrence at the treatment site (17 vs 8, mean difference 8.8, 95% CI: 2.1, 16, p = 0.013). Increasing NPV relative to total prostate volume did not improve oncologic outcomes. Baseline characteristics did not significantly differ between men with and without GGG ≥ 2 at 24-month biopsy. ALVR did not differ in men with new erectile dysfunction (mean difference in ALVR: 2.1, 95% CI: -12, 16, p = 0.8) or urinary symptoms (mean difference in ALVR 4.0, 95% CI: -21, 29, p = 0.71).

conclusionsIn patients with intermediate-risk prostate cancer, higher ALVR was associated with superior 2-year oncologic outcomes without increased risk of urinary or erectile dysfunction. KEY POINTS: Question What treatment parameters optimize focal therapy for prostate cancer by balancing healthy tissue preservation with favorable oncologic outcomes? Findings Patients without residual cancer at 24-month biopsy had twice the ALVR of those with recurrence, with no adverse impact on erectile or urinary function. Clinical relevance While fixed intra-prostatic margins (e.g., 5 mm or 10 mm) are commonly prescribed in focal therapy, this study highlights the importance of scaling the ALVR in the treatment plan to achieve sufficient oncologic coverage.