Outcomes Of Patients (Pts) With Metastatic Renal Cell Carcinoma (Mrcc) And Sarcomatoid Dedifferentiation (Srcc) After Treatment With Immune Checkpoint Inhibitors (Ici): A Single-Institution Retrospective Study.

4583Background: Pts with mRCC and sarcomatoid dedifferentiation (sRCC) have a poor prognosis with approved targeted therapies (Keskin et al. JU 2017). The response to ICIs in mRCC pts with sRCC is unknown. Methods: This is a retrospective study of pts with metastatic sRCC who received ICIs (2013-2017). Data collected include tumor histology, demographics, type of ICI, response to ICI, and efficacy outcomes (response, progression-free survival [PFS], and overall survival [OS]). Descriptive statistics were used. Results: 33 pts (85%) had clear-cell RCC (ccRCC); 6 pts had variant histology RCC (vhRCC) including chromophobe (2), mucinous tubular and spindle cell carcinoma (1), and unclassified (3). All pts but 2 had intermediate- or poor- risk disease by International Metastatic Renal Cell Carcinoma Database Consortium (IMDC) criteria. 15 pts (38%) had greater than 50% sarcomatoid component (sarc) in primary tumor of nephrectomy specimen, 5 (13%) had u003e 80%, and 2 (5%) had 100%. 22 pts (56%) received nivolumab...