Prostate Cancer Treatment in the Extreme Apex: Preservation of Continence With Robotic-Assisted MRI-Guided Transurethral Ultrasound Ablation

Purpose MRI-guided transurethral ultrasound ablation (TULSA) is a novel, minimally invasive therapy for prostate cancer designed to preserve urinary continence and erectile function. The original TULSA pivotal trial mandated preservation of 3 mm of apical tissue to protect the external sphincter. We evaluated oncologic and functional outcomes in patients with prostate cancer located at the extreme apex, including lesions abutting or involving the sphincter. Materials and methods We performed a retrospective analysis of a subgroup from a prospective TULSA cohort at a single center. Patients included had MRI-visible extreme apical lesions abutting or involving the external sphincter and ≥6 months of follow-up with prostate-specific antigen (PSA) or MRI. The extreme apex is considered to be the most distal, tapering portion of the gland adjacent to the prostatic urethral termination and membranous urethra, immediately proximal to the external urinary sphincter (rhabdosphincter). Treatment planning incorporated intraoperative diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) maps, and T2-weighted imaging. For lesions near the sphincter, a reduced 5 mm safety margin was applied, treating ≤50% of sphincter length or arc. Follow-up included serial PSA testing every three months and MRI, International Prostate Symptom Score (IPSS), and International Index of Erectile Function (IIEF) at six to nine months. Local recurrence was assessed using Prostate Imaging for Recurrence Reporting (PI-RR) criteria. Results Sixty-eight patients (61 primary and 7 salvage) were treated. Median age was 63 years, with a median follow-up of 12 months. PSA declined from a median of 7 ng/mL to 0.5 ng/mL. Among 59 patients with follow-up MRI, 88% demonstrated no evidence of disease. Six of seven patients with suspicious imaging underwent repeat TULSA, with favorable early outcomes. Functional outcomes were excellent: all patients were pad-free by three months, 80% maintained erections sufficient for penetration, and IPSS scores remained stable. Adverse events were mild and self-limited; no rectal injuries occurred. Conclusions MRI-guided TULSA is a safe and effective treatment for prostate cancer involving the extreme apical region. Despite the technical challenges posed by tumors abutting or partially involving the external urinary sphincter, carefully planned and controlled ablation - limited to ≤50% of sphincter involvement - can achieve excellent oncologic outcomes, with no evidence of residual disease on follow-up imaging and no suggestion of positive margins in treated patients. Importantly, this approach preserves urinary continence, with all patients remaining pad-free, while maintaining favorable functional outcomes. These findings support the feasibility of TULSA for the treatment of even bulky apical tumors without compromising cancer control or quality of life.