The impact of stereotactic ablative radiotherapy on oligoprogressive metastases from renal cell carcinoma

Background Renal cell carcinoma (RCC) represents 80–90% of all kidney tumors and about 15–25% of patients will develop distant metastases. Systemic therapy represents the standard of care for metastatic patients, but stereotactic ablative radiotherapy (SABR) may play a relevant role in the oligoprogressive setting, defined as the progression of few metastases during an ongoing systemic therapy on a background of otherwise stable disease. Aim of the present study was to analyze the outcome of RCC patients treated with SABR on oligoprogressive metastases. Materials and methods In this monocenter study, we analyzed patients affected by RCC treated with SABR on a maximum of 5 cranial or extracranial oligoprogressive sites of disease. Endpoints were overall survival (OS), progression-free survival (PFS), and toxicity. Results We included 74 oligoprogressions (26 intracranial and 48 extracranial) and 57 SABR treatments in 44 patients. Most common concomitant treatments were sunitinib (28, 49.1%), pazopanib (12, 21.0%) and nivolumab (11, 19.3%). Median follow-up was 19.0 months, and 1- and 2-year OS rates were 79.2% and 57.3%, respectively. Repeated SABR was a positive predictive factor for OS ( p = 0.034). Median PFS was 9.8 months, with 1- and 2-year rates of 43.2% and 25.8%. At multivariable analysis, disease-free interval ( p = 0.022) and number of treated metastases ( p = 0.007) were significant for PFS. About 80% of patients continued the ongoing systemic therapy 1- and 2-years after SABR with no grade 3 or 4 toxicities. Conclusions we confirmed the efficacy and safety of SABR for oligoprogression from RCC, with the potential to ablate resistant metastases and to prolong the ongoing systemic therapy.