Sociodemographic disparities in molecular testing for breast cancer

Molecular testing is a critical component of breast cancer care used to identify the presence of estrogen and/or progesterone receptors (jointly hormone receptors-HRs) and the expression of human epidermal growth factor 2 (HER2) on a tumor. Our objective was to characterize trends and predictors of lack of molecular testing among female breast cancer patients overall and by sociodemographic characteristics.

We examined data on female breast cancer patients diagnosed between 2010 and 2016 from Surveillance Epidemiology and End Results-18. Joinpoint regression analyses assessed annual percent change (APC) in lack of ER, PR, or HER2 testing. Multivariable, multilevel logistic regression models identified factors associated with lack of molecular testing.

A nominally lower proportion of rural patients did not receive molecular testing (e.g., 1.8% in rural vs. 2.3% in urban for HER2). For all tests, a higher proportion of Hispanic and non-Hispanic Black women were not tested. Across all characteristics, improvement in testing was noted, although disparities among groups remained. For example, lack of HER2 testing improved from 3.2 to 1.7% in White patients (APC = - 10.05) but was consistently higher in Black patients 3.9 to 2.3% (APC = - 8.21). Multivariable, multilevel models showed that older, non-Hispanic Black, and unpartnered women were at greater odds of not receiving molecular testing.

While lack of molecular testing of breast cancer patients is relatively rare, racial/ethnic, insurance status, and age-related disparities have been identified. To reduce testing and downstream treatment and outcome disparities, it is imperative for all breast cancer patients to receive molecular testing.