Disparities in HER2 testing in breast cancer.
e13084 Background: Although targeted therapies directed at human epidermal growth factor-2 (HER2) impact breast cancer outcomes, studies have found geographic variation in testing rates. We report population-based patterns of HER2 testing by patient, tumor and geographic characteristics. Methods: Retrospective analysis of Surveillance, Epidemiology, and End Results (SEER) data included women diagnosed 2010-2015 with de novo breast cancer. Women were categorized by age, race, stage, year of diagnosis, and receipt of estrogen receptor (ER), progesterone receptor (PR), and HER2 testing. SEER classified lack of testing with “test ordered, results not in chart” and “test not done.” We report on cases with HER2 “test not done”. Records missing any variables were excluded. County-level measures of socioeconomic status were included for each woman. Univariate and multivariate logistic regressions identified factors associated with testing. Results: Of 281,214 new breast cancer diagnoses, 1.75% had HER2 “test not done”. ER and PR testing were “not done” in 0.57% and 0.74% of cases, respectively. HER2-testing rates improved over time: 2.54% not tested in 2010 and 1.30% in 2015 (p < 0.01). The following characteristics were associated with higher rates of “test not done”: age >70 vs < 50 (OR = 1.33, p < 0.01), blacks vs whites (OR = 1.23, p < 0.01), Stage IV vs I (OR = 2.27, p < 0.01). Regional variation was also seen, with registries reporting HER2 “test not done” ranging from 0.18%-2.89%. On multivariate analysis (Table), HER2 testing was less likely for women age ≥ 70, blacks, Stage IV disease, and those living in counties with high rates of less than high school education. Conclusions: Rates of HER2 testing have increased. However, disparities exist and are associated with age, race, stage, geography, and education. Understanding the cause of these disparities could ultimately enhance access to appropriate therapy and improve disease outcomes. Odds of not having HER2 testing (select results from multivariate analysis). [Table: see text]