Work

Adaptive MR-guided whole-pelvic SBRT with or without focal intraprostatic lesion boost for high-risk localized prostate Cancer: Adverse events and longitudinal quality-of-life outcomes

Year: 2026

Type: article

Abstract: Purpose Evidence remains limited for combining elective pelvic nodal SBRT, online MR-guided adaptation, and simultaneous integrated boost (SIB) to intraprostatic lesion (IPL) in high-risk localized prostate cancer. We evaluated adverse events (AEs), quality-of-life (QOL), adaptive workflow, and longitudinal clinical outcomes after adaptive MR-guided whole-pelvic SBRT with or without SIB. Methods Consecutive PSMA-PET-staged patients treated on a prospective institutional protocol were analyzed. Treatment comprised 5-fraction MR-guided SBRT: 40 Gy to prostate, 33.5–35 Gy to proximal seminal vesicles, 25 Gy to elective pelvic lymphatics, and, when treated, 42.5 Gy to the IPL. Spacer use was clinician-selected. AEs were graded using CTCAE v5.0, and EPIC-50 outcomes were analyzed longitudinally. Results Seventy-seven patients were treated (median follow-up, 37.7 months); 40 (51.9%) received SIB and 34 (44.2%) received a spacer. Acute grade ≥2 (G2+) GU AE occurred in 5/76 (6.6%), with no acute G2+ GI events. Late G2+ GU and GI AEs occurred in 5/72 (6.9%) and 7/72 (9.7%), respectively. SIB was not associated with more grade ≥2 AEs. Spacer use was associated with fewer late G2+ GI AE (0/30 vs. 7/42; P = 0.0366) and better late bowel QOL. SIB was associated with lower urinary QOL at the 24-month assessment, while this finding was not observed at subsequent assessments. Biochemical recurrence, radiological recurrence, and distant metastasis occurred in 2.6%, 3.9%, and 1.3%. Conclusions Adaptive MR-guided whole-pelvic SBRT with optional SIB demonstrated favorable medium-term tolerability. These findings support the feasibility of integrating pelvic nodal SBRT, online adaptation, and focal boosting, and suggest that spacers may mitigate bowel morbidity. Prospective validation is warranted.

Source: Clinical and Translational Radiation Oncology

DOI: 10.1016/j.ctro.2026.101319