Evaluating Use Characteristics for the Oncotype Dx 21-Gene Recurrence Score and Concordance With Chemotherapy Use in Early-Stage Breast Cancer

Purpose: Oncotype Dx 21-gene assay recurrence score (RS) predicts recurrence of early-stage breast cancer (ESBC). We investigated whether patient, tumor, or practice characteristics drive its use and explored Oncotype DX RS and chemotherapy use in subgroups. Methods: Patients with ESBC with documented estrogen receptor- positive, lymph node-negative, human epidermal growth factor receptor 2-negative tumors registered within McKesson Specialty Health's iKnowMed electronic health record were included. Patient and practice characteristics by region and size were analyzed. The association between Oncotype DX RS value and use of chemotherapy were assessed. Results: The study included 6,229 patients. Of these, 1,822 (29%) had an Oncotype DX RS result. Test use was 36%, 38%, 34%, 25%, and 6%, respectively, in patients age <= 45, 46-55, 56-65, 66-75, and >= 76 years; 33%, 25%, and 9% in patients with Eastern Cooperative Oncology Group performance status of 0, 1, and >= 2; 7%, 9%, 25%, 38%, 27%, and 10% in T1mic, T1a, T1b, T1c, T2, and T3 tumors; and 26%, 32%, and 33% for grades 1, 2, and 3 tumors. Of the 1,822 patients with available Oncotype DX RS, adjuvant chemotherapy use was 6%, 42%, and 84% in the low-, intermediate-, and high-risk groups. Conclusion: Patients who were younger, had better ECOG performance status, or had higher grade tumors were more likely to undergo RS testing. It appears that the RS test may have influenced the decision about whether to administer adjuvant chemotherapy: a low RS score was associated with lower chemotherapy use and a high RS score was associated with higher chemotherapy use.