Mtor Inhibitor Therapy For Metastatic Sarcomatoid Clear Cell Renal Cell Carcinoma (Ccrcc)

450 Background: Sarcomatoid variant describes a histomorphologic pattern with presence of spindle-cell features that can be seen across all subtypes of RCC. It is associated with an aggressive phenotype and poor prognosis. Outcome to mTOR inhibitor therapy was accessed in patients (pts) with ccRCC with sarcomatoid features.Patients with metastatic sarcomatoid ccRCC treated with mTOR inhibitors at our center were retrospectively identified. Demographic characteristics and treatment outcome were assessed. Overall response rate (ORR) was determined by formal response criteria (RECIST 1.1). Progression-free survival (PFS) and overall survival (OS) were calculated using the Kaplan-Meier method.29 pts were treated with temsirolimus (18) or everolimus (11). Median age was 57 years (53 to 61) and there were 21 male pts (72%). Median number of metastatic sites was 3 (1 to 7) and 18 pts (62%) had ≥ 3 metastatic sites. Distribution between Memorial Sloan-Kettering Cancer Center risk groups was 14% favorable, 72% intermediate, and 14% poor-risk disease. Median number of prior therapies was 1 (0 to 5) and 79% of pts received mTOR inhibitor as ≥ 2(nd)-line of therapy. Three patients (10.3%) achieved a partial response (PR), 11 (38%) stable disease (SD), and 15 (51.7%) had progressive disease (PD). Tumor shrinkage was observed in 9 pts (31%) and the mean change in tumor burden was +24% (-45% to +100%). Median PFS and OS were 3.4 months (CI: 1.4-5.3) and 8.3 months (CI: 4.8- 17), respectively.OS was poor in this heterogeneous group of pts. Future studies to characterize this variant at a molecular level are warranted and might identify predictive markers for clinical outcome in patients treated with mTOR inhibitors. [Table: see text].