Prospective evaluation of three-fraction SBRT with 4D transperineal ultrasound intrafracion motion monitoring for localized prostate cancer

A prospective study at the University of Milano-Bicocca (Italy) evaluated safety and efficacy of a three-fraction SBRT regimen with real-time transperineal ultrasound guidance in localized prostate cancer. Patients received SBRT 30 Gy in three fractions. The primary endpoint was the incidence of acute and late grade ≥ 2 GU and GI adverse events. Seventy-two patients were enrolled (median age 78 years; range 56-87). The median duration of follow-up was 16 months (range 6-27).Acute grade ≥ 2 GU and GI AEs occurred in 34.7% and 8.3% of patients, respectively, and late grade ≥ 2 GU and GI AEs occurred in 13.9% and 4.2%. One acute and one late grade 3 GU event were observed, with no grade 4 or 5 AEs. Although several quality of life scores changed significantly over time, none exceeded the threshold for clinically meaningful deterioration. Median PSA declined from 7.90 to 0.44 ng/mL, and the estimated biochemical recurrence-free survival rate was 98.2% at 12 months and 96.1% at 24 months. The authors conclude that three-fraction SBRT with real-time transperineal ultrasound guidance was feasible, with severe GI and GU AEs remaining uncommon, preserved quality of life, and encouraging biochemical control in patients with localized prostate cancer. This regimen may represent a practical intermediate between conventional five-fraction SBRT and ultra-short fractionation.