390 Background: Patients treated with immune checkpoint blockade (ICB) may experience disease control without need for ongoing systemic therapy, a period not well described by conventional time-to-event endpoints. Treatment-free survival (TFS) represents a novel endpoint to quantify this period. Methods: We identified patients with mRCC from the IMDC dataset initiating first-line systemic therapy with VEGFR monotherapy (sunitinib, pazopanib), combination ICB-VEGFR therapy ([axitinib or envatinib]-pembrolizumab, cabozantinib-nivolumab, axitinib-avelumab), or ICB doublet therapy (ipilimumab-nivolumab) between February 1, 2014, and February 1, 2023. Overall survival from treatment initiation was partitioned into periods including TFS, time on first-line therapy, and survival after subsequent therapy initiation utilizing differences in restricted mean survival time (RMST) over 36-months. TFS was defined as the difference between the 36-month RMST between: (1) time from treatment initiation to discontinuation of first-line therapy, death, or censor at last follow-up and (2) time from treatment initiation to subsequent therapy initiation, death, or censor at last follow-up. Results: 3,758 patients with mRCC initiated first-line VEGFR monotherapy (n=2,635; median age 62 years; 19.1% IMDC favourable risk), ICB-VEGFR regimens (n=354; median age 60 years; 33.3% IMDC favourable risk), or doublet ICB (n=769; median age 62 years; 0% IMDC favourable risk). Patients with favourable IMDC risk initiating VEGFR monotherapy and ICB-VEGFR regimens experienced a TFS duration of 8.5% (3.1 mos 95% CI 1.5 - 4.6) and 10.1% (3.7 mos 95% CI 0.2-7.2) of the 36-month period respectively. Among intermediate/poor risk patients, those treated with VEGFR monotherapy, ICB-VEGFR regimens, and ICB doublet therapy experienced 5.9% (2.1 mos 95% CI 1.4 - 2.8), 10.3% (4.7 mos 95% CI 1.0-6.4), and 14.6% (5.3 mos 95% CI 3.8-6.8) of the 36-month period alive and treatment free respectively. Conclusions: Patients receiving VEGFR monotherapy or ICB-VEGFR combination therapies spent at most 10% of the 36-month period surviving treatment free, while IMDC intermediate/poor risk patients treated with ICB doublet therapy experienced a TFS period of 15% of the 36-month period.[Table: see text]