Treatment outcomes in patients (pts) with metastatic renal cell carcinoma (mRCC) with sarcomatoid and/or rhabdoid (S/R) features after progressive disease (PD) on immune checkpoint therapy (ICT): The MD Anderson Cancer Center experience.

351 Background: S/R mRCC is an aggressive disease that is associated with improved response to ICT. Studies performed prior to the approval of ICT demonstrated poor outcomes of S/R RCC with VEGF targeted therapies (TT). Here, we report outcomes of pts with S/R mRCC treated with VEGF TT after PD on ICT. Methods: We retrospectively reviewed the records of pts with mRCC with sarcomatoid (S), rhabdoid (R), or sarcomatoid plus rhabdoid (S+R) features who received VEGF TT after PD on ICT. Clinical endpoints of interest were time on VEGF TT and OS from treatment initiation. Directed acyclic graphs were used to identify confounders for adjustment in regression models. Hazard ratios (HR) and 95% confidence intervals (95% CI) were calculated using multivariable Cox regression. Multivariable models adjusted for epithelial histology, IMDC risk, prior VEGF TT, and inclusion of cabozantinib in the post-ICT VEGF TT regimen. Results: 57 pts with metastatic S/R RCC (52 with clear cell and 5 with non-clear cell histology) received a VEGF TT after PD on ICT. 46% of pts received a VEGF TT prior to ICT. After PD on ICT, 67% of pts had IMDC intermediate-risk disease; the most commonly used VEGF TT were cabozantinib (44%), either sunitinib, pazopanib, or axitinib (24%), and a VEGF TT in combination with an ICT (21%). Pts with R RCC had significantly longer time on VEGF TT compared with S RCC (adjusted HR = 0.45, 95% CI 0.21-0.94, p = 0.034), whereas the OS comparison was inconclusive (adjusted HR = 0.77, 95% CI 0.36-1.62, p = 0.486). IMDC risk classification following ICT progression was predictive of OS (adjusted HR = 2.22, 95% CI 1.07-4.61, p = 0.032), whereas, its association with time on VEGF TT was less conclusive (adjusted HR = 1.78, 95% CI 0.88-3.60, p = 0.107). Conclusions: Patients with S/R mRCC derive clinical benefit from VEGF TT after progression on ICT, and it is similar to the benefit previously described for patients without S/R features. Our findings suggest that the type of S/R features present and IMDC risk score inform the clinical benefit that VEGF TT will produce in this setting.[Table: see text]