Clinical outcomes of stereotactic MRI-guided adaptive radiotherapy for renal tumors in patients with a solitary kidney.

Abstract

Patients with renal cell carcinoma (RCC) in a solitary kidney have limited treatment options. Stereotactic MRI-guided adaptive radiotherapy (SMART) offers a non-invasive alternative that preserves healthy kidney tissue. This study evaluated the clinical outcomes of SMART in patients with renal tumors in a solitary kidney. Oncological outcomes, renal function preservation, and treatment-related toxicity were assessed. All consecutive patients with RCC in a solitary kidney treated with SMART between 2018 and 2024 in a single center were analyzed. Local control was defined as any response or stable disease using RECIST criteria. Kaplan-Meier analysis was used for survival outcomes and paired t-tests assessed renal function changes. Thirty-two patients with a median age of 70 years were included. Most patients had WHO status 0-1 (93.8%) and had prior nephrectomy for RCC (78.1%). Median tumor size was 4.2 cm, and median pre-treatment eGFR was 45.8 ml/min. Seven patients were treated for multiple lesions, in simultaneous or separate sessions. Most patients were treated in a single (22.8%) or five (74.3%) fractions. After a median follow-up of 21.3 months, the local control rates at 1 and 2 years were 96.2% and 90.1%, respectively. Mean eGFR change was -6.6 ml/min, none required dialysis. No grade ≥ 3 toxicity was observed. The overall survival rate at 2 years was 80.9%. SMART provides high local control with minimal impact on renal function, offering a non-invasive, kidney-sparing treatment option that also enables repeated treatments within the solitary kidney.