Discontinuing Vegf-Targeted Therapy (Vegf-Tt) For Progression Versus Toxicity Impacts Outcomes Of Second-Line Therapies In Metastatic Renal Cell Carcinoma (Mrcc).

503 Background: A significant minority of mRCC patients prematurely discontinue first-line (1L) VEGF-TT due to toxicity. Whether clinical outcomes differ in patients receiving second line (2L) TT based on reason for discontinuation of 1L are unknown. Methods: Patients from 15 International mRCC Database Consortium (IMDC) centers who started 2L TT were included and the reason for discontinuation of 1L collected. Treatment outcomes of 2L, including response, time to treatment failure (TTF) and overall survival (OS) were assessed. Results: 1124 patients were identified: 866 patients (77%) discontinued 1L VEGF-TT due to progression, 208 patients (19%) due to toxicity. 50 patients (4%) who discontinue due to other reasons were excluded. The reason for discontinuation of 1L did not differ by IMDC risk group at start of 1L VEGF-TT (p=0.54) or 2L therapy (p=0.52). Median time from 1L VEGF-TT initiation to start of 2L in patients who progressed or stopped prematurely due to toxicity was 9.8 and 7.9 months, respect...