ESTRO 2023 - Abstract Book

S1084

Digital Posters

ESTRO 2023

PO-1353 MR-Guided stereotactic radiotherapy for pancreatic oligometastases from renal cell carcinoma

J. van Vulpen 1 , H. Eijkelenkamp 1 , G. Meijer 1 , M. Intven 1

1 UMC Utrecht, Radiation Oncology, Utrecht, The Netherlands

Purpose or Objective Patients with pancreatic metastases from clear cell renal cell carcinoma (RCC) have been reported to have an extraordinarily favourable prognosis. Traditionally, treatment for these pancreatic oligometastases comprises either surgical resection or systemic therapy. However, SBRT may be an effective, non-invasive alternative strategy, provided that it shows good local control rates and acceptable toxicity among treated patients. Materials and Methods We reviewed all patients treated with MR-guided SBRT for pancreatic oligometastases from renal cell carcinoma at the University Medical Center Utrecht. We explored freedom from local progression (FFLP), progression-free survival (PFS), freedom from start of systemic therapy (FFST), and adverse events (AEs) among treated patients. The Kaplan-Meier method was used to describe the time-to-event endpoints, with estimates at 1 year calculated using logarithmic transformation of the survival function. FFLP was assessed per lesion, adding patient as a cluster effect. Results From June 2019 to September 2022, we identified 11 patients treated with MR-guided SBRT 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. At a current median follow-up of 9.5 months (range 1-42 months), estimated FFLP at 1 year was 87% (95% CI 66-100%). 1y-PFS was 83% (95% CI 58-100%), and 1y-FFST was 100%. No grade ≥ 3 AEs were observed.