Outcomes of treatment cessation in select metastatic renal cell carcinoma (mRCC) patients.

4521 Background: Tyrosine kinase inhibitors (TKIs) demonstrate efficacy in mRCC, but may cause significant adverse effects (AEs). We have previously evaluated outcomes in patients (pts) receiving prolonged treatment breaks on TKIs and expand and update this experience herein. Methods: mRCC pts on targeted therapy who discontinued treatment for ≥3 months were analyzed retrospectively. Treatment break was defined as a period of drug cessation for reasons other than progressive disease. Pts could receive treatment breaks with multiple lines of therapy (defined sequentially as treatment A, B, C etc.) A number of patients continue on treatment/observation, hence durations were estimated using the Kaplan-Meier method. Results: Baseline characteristics (n=112) were: 75% male; median age at diagnosis 56; 95% clear cell. 19% pts had received prior systemic therapy. 48% pts were favorable, 48% intermediate and 4% poor risk by Heng criteria. Table 1 depicts outcomes with sequential lines of therapy. Overall, pts rec...