Background: By 2018, seven Immune Checkpoint Inhibitor (ICI) drugs had gained FDA approval in nine cancers and the number of indications has continued to increase. Haslam et al. estimated that between 36.1 and 38.5% of US patients with cancer were eligible for ICI therapy in 2019. We report the use of ICI dugs in the first-line of therapy (LOT1) and second-line (LOT2) among enrollees treated for 9 cancers with an FDA indication approval in or before 2017. Methods: A cohort of patients treated for one of the nine most common cancers with an FDA indication for ICI drugs in 2017 was identified using de-identified data from the OptumLabs Data Warehouse, and clinical information from the Optum Cancer Guidance Program’s electronic prior authorization (ePA) platform. De-identified administrative claims data were then linked to ePA information (cancer type & diagnosis date) at the patient level to identify details of treatment received. Eligible patients were enrolled in a commercial or Medicare Advantage (MA) plan and initiated treatment within six months of diagnosis, enrolled at least six months prior to diagnosis date (ensuring this was the LOT1) and at least thirty days after start of first identified treatment regimen (to identify the full treatment regimen). LOT1 treatment initiation ranged from 1/1/2017 to 12/31/2020 for those who were diagnosed before 6/30/2020. ICI regimens are defined as those with an ICI drug received within first thirty days of the LOT start date. Results: In this population, we identified 17,283 eligible patients treated for non-small cell lung cancer (4654), melanoma (705), renal cell carcinoma (554), bladder cancer (1974), colorectal (4502), hepatocellular carcinoma (673), gastric cancer (1786), head and neck cancer (1923), or Hodgkin lymphoma (512) in 2018, 2019, and 2020. Overall, 3,291 (19%) of these patients received an ICI in LOT1 with rates increasing over time. The highest rates of ICI use in LOT1 are for the treatment of melanoma, remaining consistent over time, while ICI use in LOT2 is highest for the treatment of non-small cell lung cancer although evidence from 2020 suggests this may be waning. Among patients being treated for renal cell carcinoma, ICI use in LOT2 decreased from 43% (2018) to 15% (2020) while LOT1 ICI use increased to 81% in 2020. Conclusions: Overall, ICI use has changed over time in both the first- and second-line setting. In particular, we observe a shift in ICI use from LOT2 to LOT1, consistent with the more recent FDA approvals in earlier lines of therapy.

*2020 data for those diagnosed through 6/30/2020.