PDGFRB and collecting duct carcinoma: The addition of sorafenib (inhibitor of VEGFR1-3, PDGFR, and RAF kinases) to chemotherapy was studied in a single-arm phase 2 study that showed an mPFS of 8.8 mo (95% CI 6.7–10.9 mo) and ORR of 30.8% in 26 patients with collecting duct carcinoma.