Racial disparities and utilization trends of first-line targeted therapies for metastatic breast cancer

We aimed to determine temporal trends and racial disparities in utilization and time to treatment initiation of cyclin dependent kinase 4/6 (CDK4/6) inhibitors and pertuzumab for first-line metastatic breast cancer.

We extracted data from a nationwide electronic health record-derived deidentified database. Female patients aged 18 years and older with estrogen receptor-positive and HER2-negative or HER2-positive metastatic breast cancer eligible for CDK4/6 inhibitors (March 2015-October 2021) or pertuzumab (July 2012-September 2021) were included. Our outcomes were adjusted temporal trends in the proportion of patients receiving respective therapies using logistic regression with natural cubic splines for time trends and tested for changes in utilization over time within and between racial groups (non-Hispanic White or non-Hispanic Black). Similar models using linear regression estimated mean time to treatment initiation.

A total of 5173 (non-Hispanic White = 4478; non-Hispanic Black = 695) estrogen receptor-positive and HER2-negative and 2321 (non-Hispanic White = 1915; non-Hispanic Black = 406) HER2-positive metastatic breast cancer patients were included. There were statistically significant differences in the proportion initiating CDK4/6 inhibitors over time within racial groups (non-Hispanic White: 23.5%, 95% confidence interval [CI] = 20.1% to 27.3%, in 2015 to 53.8%, 95% CI = 48.6% to 59.0%, in 2021; non-Hispanic Black: 20.6%, 95% CI = 11.9% to 33.0%, in 2015 to 73.6%, 95% CI = 61.7% to 83.0%, in 2021) and between groups (P = .009). There was a statistically significant increase in utilization of pertuzumab within both racial groups over time (P < .001), but no statistically significant difference between groups (P = .45). Time to treatment initiation decreased over time with no statistically significant differences in time to treatment initiation trends between the 2 groups.

Utilization of targeted therapies increased over time, however non-Hispanic Black patients were less likely to receive CDK4/6 inhibitors compared with non-Hispanic White. Approximately half of eligible patients did not receive pertuzumab. Further research is needed to understand mediators and design interventions to address underutilization of these therapies and those contributing to racial disparities in CDK4/6 inhibitor utilization.