Magnetic resonance-guided radiotherapy (MRgRT) applied as stereotactic body radiotherapy to the prostate bed represents an emerging post-prostatectomy treatment approach, offering superior soft-tissue visualization and the potential for daily online adaptive planning. This study reports a prospective experience with MR-guided adaptive SBRT to the prostate bed, with a primary focus on treatment-related adverse events and patient-reported quality-of-life (QoL) outcomes.
A prospective cohort of 31 patients with biochemical recurrence following radical prostatectomy was treated with MR-guided adaptive SBRT (32.5 Gy in 5 fractions) using a 0.35 T MR-LINAC (MRIdian®, ViewRay). Elective pelvic nodal irradiation was delivered in 42% of patients (25 Gy in 5 fractions), and a simultaneous integrated boost (SIB) to macroscopic disease (35 Gy in 5 fractions) was administered in 9.7% of cases. Concomitant androgen deprivation therapy (ADT) was administered in 77.4% of patients. Adverse events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0, and patient-reported outcomes were assessed using the Expanded Prostate Cancer Index Composite-26 (EPIC-26) and the International Prostate Symptom Score (IPSS).
With a median follow-up of 8.8 months (IQR: 6.1-16.8), no grade ≥ 3 adverse events were observed at any time point. Acute grade ≥ 2 genitourinary (GU) adverse events were 3.3% at treatment completion (1/30) and 4.3% at 6 months (1/23), with low-grade urinary incontinence as the predominant event. "No grade ≥ 2 gastrointestinal (GI) adverse events were observed throughout the follow-up period.EPIC-26 urinary domain scores were preserved over time (baseline: 79.6; 6 months: 81.5), while bowel domain scores remained consistently at ceiling levels (median 100 points at all time points). Median prostate-specific antigen (PSA) declined from 0.31 ng/mL pre-treatment to 0.02 ng/mL at 6 months, with continued suppression at 12 months (0.04 ng/mL, n = 11). Biochemical response was 100% (31/31), although interpretation is limited by the short follow-up.
MRgRT to the prostate bed demonstrates a favorable early safety and tolerability profile, with no grade ≥ 3 adverse events, low rates of grade ≥ 2 GU adverse events (4.3% at 6 months, 1/23), and absence of late grade ≥ 3 GI adverse events, while maintaining patient-reported QoL outcomes.
Clinical and translational radiation oncology. 2026 Jul 25*** epublish ***
Daniela Gonsalves Pieretti, Fernando López-Campos, Abrahams Ocanto, Maria González, Lisselott Torres, Castalia Fernandez, Gloria Sanchez, Gloria Guardia, Alvaro Flores, Jon Andreescu, Laura Viduera, Dulce Urias, Ofelia Cabanes, Julia Rogriguez, Sigfredo Elias Romero Zoghbi, Jose Antonio González, Miren Gaztañaga, Luis Glaria, Maia Dzhugashvili, Stefano Arcangeli, Federica Ferrario, Juan Ignacio Martinez Salamanca, Giulio Francolini, Felipe Couñago
Department of Radiation Oncology, GenesisCare-Vithas La Milagrosa University Hospital, 28010 Madrid, Spain., Department of Radiation Oncology, GenesisCare Campo Gibraltar, 11370 Algeciras, Spain., Department of Radiation Oncology, GenesisCare Hospital San Juan de Dios, 14012 Cordoba, Spain., Department of Radiophysics, GenesisCare-Vithas La Milagrosa University Hospital, 28010 Madrid, Spain., Department of Radiation Oncology, Instituto Nacional de Cancerología, 14080 Ciudad de Mexico, Mexico., Department of Radiation Oncology, GenesisCare Talavera de la Reina, 45600 Talavera de la Reina, Spain., Department of Radiation Oncology, GenesisCare Sevilla, 41092 Sevilla, Spain., Department of Radiation Oncology, GenesisCare-San Francisco de Asís University Hospital, 28002 Madrid, Spain., School of Medicine and Surgery, University of Milan Bicocca, Milan, Italy., Radiation Oncology, Fondazione IRCCS San Gerardo dei Tintori, Monza, Italy., Department of Urology, Lyx Institute of Urology, Universidad Francisco de Vitoria, 28223 Madrid, Spain.