MR-Guided Stereotactic Ablative Body Radiotherapy for Pancreatic Oligometastases from Renal Cell Carcinoma

Abstract

Patients with pancreatic metastases from renal cell carcinoma (RCC) have been reported to have an unusually favorable prognosis. Traditionally, treatment for these pancreatic oligometastases comprises either surgical resection or systemic therapy. However, stereotactic ablative body radiotherapy (SAbR) may be an effective, non-invasive alternative strategy, provided that it shows acceptable toxicity and high local control rates among treated patients. We reviewed all patients treated with MR-guided SABR for pancreatic oligometastases from renal cell carcinoma at a single institute. We explored adverse events (AE), freedom from local progression (FFLP), progression-free survival (PFS), and freedom from start of systemic therapy (FFST) among treated patients. The Kaplan-Meier method was used to describe the time-to-event endpoints. From June 2019 to September 2022, we identified 11 patients treated with MR-guided SAbR to 31 pancreatic oligometastases from RCC. Patients had a mean age of 65.6 years (±6.8) and had a median of 3 irradiated pancreatic metastases (range 1-7). Metastases were treated with 5 fractions of 7 Gy (n = 1 metastasis) or 8 Gy (n = 30 metastases) per fraction. One grade 3 adverse event (bleeding) was observed. At a median follow-up of 10.5 months (range 5-46 months), estimated FFLP at 1 year was 100%. 1y-PFS was 83% (95% CI 58-100%), and 1y-FFST was 91% (95% CI 75-100%). First exploration of MR-guided SAbR to pancreatic oligometastases from RCC indicates that it can be an effective and safe treatment option. Moreover, MR-guided SAbR may facilitate deferral of systemic therapy initiation in this select group of patients with favorable prognosis.