Stereotactic Ablative Radiotherapy for the Treatment of Pancreatic Metastases from Renal Cell Carcinoma

Abstract

<h3>Purpose/Objective(s)</h3> Glandular metastases, in particular pancreatic metastases, are associated with renal cell carcinoma (RCC) of indolent biology. Pancreatic metastases may develop in isolation or involve other organs and are associated with prolonged survival. Pancreatic metastases can be treated with systemic therapy, stereotactic ablative radiotherapy (SAbR) or surgical resection and the optimal management of these patients is unknown. There is a paucity of data on SAbR for RCC pancreatic metastases. Here, we report local control (LC), progression-free survival (PFS), overall survival (OS) rates as well as toxicities related to SAbR for RCC metastases to the pancreas. <h3>Materials/Methods</h3> This IRB-approved, single-institution, retrospective study included patients with RCC metastases to the pancreas treated with SAbR. Data on patient demographics, functional status, tumor characteristics, International Metastatic RCC Database Consortium (IMDC) risk category, local and systemic treatments, toxicities, and outcomes were collected and analyzed. RECIST 1.1 principles were utilized to determine LC rates and PFS. PFS was defined from the initiation of SAbR to progression (at SAbR-treated or other sites), or death. OS was defined from the start of SAbR to death. Two independent reviewers assessed patient electronic health records for toxicities using CTCAE v5 and relatedness scores. <h3>Results</h3> Twenty pancreatic metastases were treated with SAbR in sixteen RCC patients including 11 (69%) with favorable and 5 (31%) with intermediate-risk IMDC scores. Three patients (19%) were treatment naïve with oligometastatic disease, and thirteen (81%) were oligo-progressive on systemic therapy with 1-3 lines of prior systemic therapy. With a median follow-up of 35.9 months, LC was 90%. The two local failures observed occurred at 31.6 and 78.8 months following SAbR treatment. The median PFS was 12 months, 95% CI (3.3, 18.8), and the 2-year overall survival following pancreatic SAbR was 100%. The most common total dose and fractionation regimen utilized was forty Gray delivered over five fractions. The percentage of patients experiencing an acute grade 2 or 3 toxicity attributed to pancreatic SAbR was 6%. There was no acute grade >3 toxicities. The percentage of patients experiencing a late grade 2 or 3 toxicity was 12%. Median time to late adverse events was 42.5 months. <h3>Conclusion</h3> SAbR of RCC metastases to pancreas is feasible, safe and appears to be effective. Median PFS and 2-year OS in this cohort compared favorably to those reported in historical cohorts and is consistent with indolent disease.