Prospective Evaluation of the Impact of the 21‐Gene Recurrence Score Assay on Adjuvant Treatment Decisions for Women with Node‐Positive Breast Cancer in Ontario, Canada

BACKGROUND: The 21-gene Recurrence Score (RS) assay is only reimbursed in Ontario for node-negative and micrometastatic node-positive (N+) early-stage breast cancer (EBC). We carried out a prospective study to evaluate the impact of the assay on treatment decisions for women with N+ EBC. SUBJECTS, MATERIALS, AND METHODS: Women with estrogen receptor-positive, human epidermal growth receptor 2-negative EBC and one to three positive axillary lymph nodes, who were candidates for adjuvant chemotherapy in addition to hormonal treatment, but in whom the benefit of chemotherapy was uncertain, were eligible. The primary objective was to characterize how the results of the RS assay affected physicians' recommendations for adjuvant chemotherapy. Secondary objectives were to characterize changes in the physicians' and patients' level of confidence in treatment recommendations, to determine whether the results of the RS assay affected patients' treatment preferences, and to determine the final treatment administered. RESULTS: Seventy-two patients were recruited; the mean age was 61. RS was <18 in 55%, between 18 and 30 in 36%, and ≥31 in 9% of patients. Treatment recommendations changed in 36% of all evaluable patients. The most significant change was in the group with a low RS. Physicians' and patients' confidence in treatment recommendations increased in 49% and 54% of cases, respectively. Upfront chemotherapy was recommended to 79% of patients before the assay; 42% ultimately received chemotherapy. CONCLUSION: The RS assay resulted in a substantial decrease in the number of patients who received chemotherapy and in an increase in physicians' and patients' confidence in the adjuvant treatment recommendations. IMPLICATIONS FOR PRACTICE: This is the first decision impact study to include exclusively women with ER-positive, HER2-negative, early-stage breast cancer with 1-3 positive lymph nodes, a population typically treated with adjuvant chemotherapy. This study provides evidence that, in these patients, the Oncotype Dx Recurrence Score assay influences systemic treatment decisions. Most of the changes in treatment recommendation resulted in withdrawal of chemotherapy or change in recommendation from a chemotherapy regimen with anthracyclines to a taxane-only regimen. If prospective studies confirm that these decisions result in good outcomes, a reduction in the use of chemotherapy might result in pharmacoeconomic savings.