21-Gene recurrence score testing among Medicare beneficiaries with breast cancer in 2010-2013

Purpose: We evaluated national patient-level utilization of the 21-gene recurrence score (21-gene RS) test among Medicare beneficiaries with breast cancer. We analyzed clinical, demographic, and regional factors that predict testing. Methods: Using 2010-2013 Medicare claims, we conducted a retrospective study of breast cancer patients. The outcome variable was whether the patient underwent testing. Independent variables expected to predict testing were age, gender, race, Medicaid status, clinical characteristics, and hospital referral region (HRR). Results: From 2010 to 2013, the number of test orders increased by 23.0%. Of the 256,818 patients identified in 2011-2012 claims, 25,352 (9.9%) underwent the 21-gene RS test. Estrogen receptor-positive status was the strongest positive predictor of testing (odds ratio (OR) 2.58, 95% confidence interval (CI) 2.48-2.69). White patients were more likely to be tested than minorities (OR 1.46, 95% CI 1.39-1.52). Secondary cancer was the strongest negative predictor. Medicaid recipients were less likely to be tested (OR 0.74, 95% CI 0.71-0.78). The likelihood of testing decreased with increasing age and comorbidities. Conclusions: Despite widespread implementation of the 21-gene RS test, minorities and Medicaid recipients had less access to testing. Many patients with serious comorbidities or advanced age were tested even though the risk algorithm may not have been applicable to them.