LAUSR

398 Background: The treatment landscape for mRCC has evolved in recent years with the use of tyrosine kinase inhibitors (TKI) and immuno-oncology (IO) therapies. This study examined patient characteristics, treatment patterns, costs, and survival for individuals with mRCC who received either IO-IO or IO+TKI as first-line (1L) regimens. Methods: This retrospective cohort study used an administrative claims dataset from a commercial health plan integrated with clinical data from a cancer care quality program (CCQP) and socioeconomic data from national surveys. Eligible patients began treatment for mRCC between 04/01/2018 and 1/31/2023, were aged ≥ 18 years old, and had ≥ 6 months of health plan enrollment prior to and ≥ 1 month after their 1L treatment. Patient characteristics and 1L and second-line (2L) regimens were described. Costs were summarized per patient per month (PPPM) within time intervals. The Kaplan-Meier method was used to estimate treatment-free interval (TFI) and survival times. Results: The study identified 824 eligible mRCC patients; mean age was 60, 77% were male, and 85% White/6% Black race. Patients receiving 1L IO-IO (n = 471; nivolumab plus ipilimumab) or IO+TKI regimens (n = 353; pembrolizumab plus axitinib [63.7%], nivolumab plus cabozantinib [21.8%], pembrolizumab plus lenvantinib [14.4%]) had similar baseline characteristics with the exception of health plan type, body mass index, and risk score (Table 1). As 2L therapy, patients most often received TKI monotherapy (56%) or IO+TKI (26%). Treatment costs were higher for IO-IO in the first 3 months but lower in subsequent time intervals compared with IO+TKI. Medication costs represented 80% of total costs on average. Between IO-IO and IO+TKI arms, median TFI (1.1 and 1.2 months, respectively) and cumulative survival time (75.1% and 78.3% at 12 months, respectively) were similar. Conclusions: The study described treatment patterns for mRCC and found patients receiving 1L IO-IO and IO+TKI regimens were similar demographically, though IO-IO patients started with poorer risk scores. Although IO-IO was associated with higher treatment costs in the first 3 months, the subsequent monthly costs were lower vs IO+TKI. Results also indicated that retreatment with IO in the 2L setting is occurring in real-world practice.[Table: see text]