Clinical Outcomes in Early Breast Cancer With a High 21-Gene Recurrence Score of 26 to 100 Assigned to Adjuvant Chemotherapy Plus Endocrine Therapy A Secondary Analysis of the TAILORx Randomized Clinical Trial

Importance A high 21-gene recurrence score (RS) by breast cancer assay is prognostic for distant recurrence of early breast cancer after local therapy and endocrine therapy alone, and for chemotherapy benefit. Objective To describe clinical outcomes for women with a high RS who received adjuvant chemotherapy plus endocrine therapy in the TAILORx trial, a population expected to have a high distant recurrence rate with endocrine therapy alone. Design, Setting, and Participants In this secondary analysis of data from a multicenter randomized clinical trial, 1389 women with hormone receptor-positive, ERBB2-negative, axillary node-negative breast cancer, and a high RS of 26 to 100 were prospectively assigned to receive adjuvant chemotherapy in addition to endocrine therapy. The analysis was conducted on May 12, 2019. Interventions The adjuvant chemotherapy regimen was selected by the treating physician. Main Outcomes and Measures Freedom from recurrence of breast cancer at a distant site, and freedom from recurrence, second primary cancer, and death (also known as invasive disease-free survival [IDFS]). Results Among the 9719 eligible women, with a mean age of 56 years (range 23-75 years), 1389 (14%) had a recurrence score of 26 to 100, of whom 598 (42%) had an RS of 26 to 30 and 791 (58%) had an RS of 31 to 100. The most common chemotherapy regimens included docetaxel/cyclophosphamide in 589 (42%), an anthracycline without a taxane in 334 (24%), an anthracycline and taxane in 244 (18%), cyclophosphamide/methotrexate/5-fluorouracil in 52 (4%), other regimens in 81 (6%), and no chemotherapy in 89 (6%). At 5 years, the estimated rate of freedom from recurrence of breast cancer at a distant site was 93.0% (standard error [SE], 0.8%), freedom of recurrence of breast cancer at a distant and/or local regional site 91.0% (SE, 0.8%), IDFS 87.6% (SE, 1.0%), and overall survival 95.9% (SE, 0.6%). Conclusions and Relevance The estimated rate of freedom from recurrence of breast cancer at a distant site in women with an RS of 26 to 100 treated largely with taxane and/or anthracycline-containing adjuvant chemotherapy regimens plus endocrine therapy in the prospective TAILORx trial was 93% at 5 years, an outcome better than expected with endocrine therapy alone in this population. Question What is the prognosis in early breast cancer associated with a high 21-gene recurrence score when treated with adjuvant chemotherapy plus endocrine therapy? Findings In this secondary analysis of a randomized clinical trial, among 1389 women with early breast cancer and a high score of 26 to 100 by 21-gene assay who received adjuvant chemotherapy, the estimated proportion free from distant recurrence at 5 years was 93%. Meaning In women with hormone receptor-positive, ERBB2-negative, axillary node-negative breast cancer, and a high 21-gene recurrence score, a higher proportion were free from distant recurrence when treated with chemoendocrine therapy than expected with endocrine therapy alone. This secondary anaysis of the TAILORx randomized clinical trial describes clinical outcomes for women with a high 21-gene recurrence score who received adjuvant chemotherapy plus endocrine therapy, a population expected to have a high distant recurrence rate with endocrine therapy alone.