A Pilot Study to Evaluate Trans-Rectal, Outpatient Magnetic Resonance Thermal Image-Guided Laser Focal Therapy of Prostate Cancer: Results of the First 112 Treatments

Background/Objectives: In the United States alone, new prostate cancer (PCa) cases for 2023 are estimated at 288,300 and deaths at 34,13700 [1]. Prostate imaging is increasingly evaluated by artificial intelligence and computer-assisted targeting which opens new opportunities in biopsy and the focal therapy of visualized lesions [2]. Our objective was to investigate the safety and feasibility of using MR-guided focal laser (light amplification by the stimulated emission of radiation) therapy for these visible cancers using a transrectal approach for both laser applicator placement and therapy delivery in an outpatient setting. Methods: We used a 1.5 Tesla MRI scanner (Philips Healthcare, Best, The Netherlands) for both image acquisition and real-time thermometry. In addition, we used a commercially available CAD system and targeting hardware (Philips, Best, The Netherlands) for image analysis and interventional planning. Laser focal therapy of biopsy-proven lesions was delivered using a U.S. Food and Drug Administration (FDA) 510(k) cleared laser emitter, laser fiber and thermal mapping visualization software (Medtronic, Minneapolis, MN, USA) introduced transrectally under MRI-guidance. Results: 112 cancer foci were treated in 81 men, from Gleason Grade 1 (GG1) to GG3 for treatment-naïve patients and all Gleason Grades for salvage patients. With pre-treatment lesion volumes ranging from 0.03 cc to 6.6 cc, with a mean of 1.1 cc and a median of 0.49 cc (25% and 75% quartiles of 0.25 cc and 1.4 cc respectively). The mean MRI volume of coagulation necrosis was 7.1cc and ranged from 0.6cc to 22.9cc. No serious adverse events or morbidity were reported. At six-month MR-guided in-bore biopsy 25 treatment regions were positive for clinically significant disease (GG>1), consistent with in-field residual or recurrent cancer rate of 22% of regions and 23% of subjects. We observed a 40% decrease in mean PSA at 1 year post therapy in the entire cohort. Conclusions: Our data indicate that transrectally delivered MRI-guided laser focal therapy for prostate cancer is both safe and feasible in an outpatient setting and results in a significant biochemical response and acceptable cancer control rate at 6 months.