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

Abstract

Glandular metastases including pancreatic and adrenal sites of disease are associated with renal cell carcinoma (RCC) of indolent biology. Adrenal and pancreatic metastases may develop in isolation or involve other organs and are associated with prolonged survival. Glandular 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 paucity of data on SAbR for RCC glandular metastases. We hypothesize that ablative doses of radiation therapy utilizing SAbR are associated with high rates of local control greater than 90%, with minimal or no acute grade 3 toxicities or higher with this approach. 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 pancreatic and adrenal glands. This IRB-approved, single-institution, retrospective study included patients with RCC metastases to the adrenal glands and 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 principals were utilized to determine LC rates and PFS. PFS was determined 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 these measures and analyzed patient electronic health records for toxicities using CTCAE v5 and relatedness scores. A total of 50 RCC patients were included in this study with 36 adrenal and 20 pancreatic metastases treated with SAbR. Median dose fractionation used was 40 Gray delivered in 5 fractions. Sixteen patients (32%) were treatment naïve with oligometastatic disease, and thirty-four (68%) were oligo-progressive on systemic therapy with 1-3 prior lines of systemic therapy. For treated adrenal metastatic lesions at 1 year, patients demonstrated a 75.3% OS, 46.7% PFS, and LC of 93.3%. For treated pancreatic metastatic lesions at 1 year, patients demonstrated a 100% OS, 48.6% PFS, and LC of 100%. At 1 year, there was an OS of 82.2%, PFS of 48.2%, and LC of 95.9 % in the combined cohort. The percentage of patients experiencing an acute grade 2 or 3 toxicity attributed to adrenal or pancreatic gland SAbR was 7.4%. There were no acute grade >3 toxicities. The percentage of patients experiencing a late grade 2 or 3 toxicity was 9.3%. Median time to late adverse events was 37.4 months. SAbR of RCC metastases to the pancreas and adrenal glands is feasible, safe and appears to be effective. Median PFS and OS in this cohort compared favorably to those reported in historical cohorts and is consistent with indolent disease.