Utilization of Immunotherapy in Patients with Cancer Treated in Routine Care Settings: A Population-Based Study Using Health Administrative Data

Abstract Introduction The introduction of immunotherapy (IO) in the treatment of patients with cancer has significantly improved clinical outcomes. Population level information on actual IO utilization is limited. Methods We conducted a retrospective cohort study using provincial health administrative data from Ontario, Canada to: (1) assess the extent of IO use from 2011 (pre-IO funding) to 2019; and (2) identify factors associated with IO use in patients with advanced cancers for which IO is reimbursed including melanoma, bladder, lung, head and neck, and kidney tumors. The datasets were linked using a unique encoded identifier. A Fine and Gray regression model with death as a competing risk was used to identify factors associated with IO use. Results Among 59 510 patients assessed, 8771 (14.7%) received IO between 2011 and 2019. Use of IO increased annually from 2011 (3.3%) to 2019 (39.2%) and was highest in melanoma (52%) and lowest in head and neck cancer (6.6%). In adjusted analysis, factors associated with lower IO use included older age (hazard ratio (HR) 0.91 (95% CI, 0.89-0.93)), female sex (HR 0.85 (95% CI, 0.81-0.89)), lower-income quintile, hospital admission (HR 0.78 (95% CI, 0.75-0.82)), high Charlson score and de novo stage 4 cancer. IO use was heterogeneous across cancer centers and regions. Conclusion IO utilization for advanced cancers rose substantially since initial approval albeit use is associated with patient characteristics and system-level factors even in a universal healthcare setting. To optimize IO utilization in routine practice, survival estimates and potential inequity in access should be further investigated and addressed.