Factors Associated with Adoption of Immune Checkpoint Inhibitor Treatment for Advanced Melanoma: A SEER-Medicare Cohort Study

Abstract

We aimed to explore the differences in immune checkpoint inhibitor (ICI) immunotherapy utilization for advanced melanoma by examining patient and neighborhood characteristics. We performed a retrospective cohort study using a deidentified, random sample of SEER-Medicare beneficiaries aged ≥65 years with stage III or stage IV melanoma (2011–2017). Our primary outcome was initiation of ICI immunotherapy (ipilimumab, pembrolizumab, nivolumab, or atezolizumab) after stage III or stage IV melanoma diagnosis. We analyzed ICI usage with multivariable logistic regression. After analyzing the entire 2011–2017 cohort, we conducted a secondary analysis in which we separately analyzed the 2011–2014 and 2015–2017 cohorts to assess possible differences over time. We included 3531 beneficiaries, with mean follow-up of 2.1 (SD = 2.0) years. Higher likelihood of ICI usage was associated with male sex (OR = 1.21, 95% confidence interval = 1.04–1.42) and higher density of medical oncologists (OR = 1.02, 95% confidence interval = 1.01–1.04). Lower likelihood of ICI usage was associated with older age group and Charlson comorbidity score (score ≥2; OR = 0.72, 95% confidence interval = 0.60–0.86). These associations were diminished in more recent years (no association with sex, medical oncologist density, Charlson comorbidity score, and association with only the oldest age group in years 2015–2017). We found significant sex- and age-related differences in initiation among SEER-Medicare beneficiaries with stage III or stage IV melanoma, which appear to be improving over time.