Stereotactic ablative radiotherapy: an effective alternative for pancreatic metastases originating from renal cell carcinoma-experience from two European institutions.

Pancreatic metastases from renal cell carcinoma (RCC) are associated with a favorable prognosis in oligometastatic disease. Stereotactic ablative radiotherapy (SABR) offers a non-invasive alternative to surgery. Given the limited data in literature, we report our experience using SABR in RCC patients presenting with pancreatic oligometastases. A retrospective analysis was conducted from 2017 to 2023 in two European institutions. SABR was delivered using Volumetric Modulated Arc Therapy or Magnetic Resonance-guided technique. Local control (LC), progression-free survival (PFS), overall survival (OS), toxicity and factors impacting on survival were explored. Thirty-three patients with 46 pancreatic metastases were included. Median time to pancreatic metastases development was 12 years from nephrectomy. Median size of lesions was 16 mm and SABR dose ranged between 35 and 45 Gy in 5–6 daily fractions. At median follow-up of 25 months, four patients experienced local progression. LC rates at 1, 2 and 5 years were 100%, 89% and 76%, respectively. Median time to best local response was 9 months, with partial/complete response in 58% of patients. The 1- and 5-year OS rates were 97% and 79%, respectively. Median PFS was 23 months. Size of pancreatic metastasis was significantly correlated with PFS. After SABR, median time to new therapy was 27 months. Overall, one patient had late G3 pancreatitis and no ≥G4 events were seen. In this analysis, the largest ever reported, SABR was a safe and effective treatment for pancreatic metastases from RCC, yielding a remarkable local control with minimal toxicities and delaying the subsequent systemic therapy.