Upper Urinary Tract Stereotactic Body Radiotherapy Using a 1.5 Tesla Magnetic Resonance Imaging-Guided Linear...

Area of Science:

• Oncology
• Radiotherapy
• Medical Imaging

Background:

• Radiotherapy technology advances allow ablative doses for upper urinary tract (UUT) targets, including renal cell carcinoma (RCC) and upper tract urothelial carcinomas (UTUC).
• Magnetic resonance imaging-guided linear accelerators (MR-Linacs) offer enhanced precision and adaptability for stereotactic body radiotherapy (SBRT).

Purpose of the Study:

• To evaluate the feasibility, safety, and efficacy of MR-Linac-based SBRT for upper urinary tract lesions.
• To assess the impact of online adaptation strategies (ATP and ATS) on treatment duration and toxicity.

Main Methods:

• Retrospective analysis of 34 patients treated with MR-Linac SBRT (August 2020-September 2024).
• Included 31 primary UUT non-metastatic tumors (RCC/UTUC) and 3 metastases.
• Employed "adapt-to-position" (ATP) and "adapt-to-shape" (ATS) online adaptation with compression belts for motion management.

Main Results:

• Median treatment duration was 56 minutes; ATP was significantly shorter (54 min) than ATS (80 min).
• 77% of patients experienced self-resolving grade 1-2 acute toxicity; no grade ≥ 3 acute toxicity.
• Late toxicity included grade 1-2 in 9% and grade 3 in 3% of participants.

Conclusions:

• MR-Linac-based SBRT with online plan adaptation is a feasible and safe treatment for UUT lesions.
• This modality provides high precision for definitive management of select upper urinary tract cancers.
• Low toxicity rates support its clinical utility in managing RCC and UTUC.