CHICAGO – Docetaxel plus cyclophosphamide was significantly inferior to treatment with anthracycline/taxane-based chemotherapy, according to an interim joint analysis of the ABC (anthracyclines in early breast cancer) trials.
The ABC trials are three sequential trials from the US Oncology Research and National Surgical Adjuvant Breast and Bowel Project that randomized women with resected high-risk, early-stage breast cancer to receive docetaxel plus cyclophosphamide (TC) or one of several standard anthracycline/taxane-based chemotherapy (TaxAC) regimens.
A total of 4,130 patients met the ABC trials’ eligibility requirements and were randomly assigned to receive either TC therapy (n = 2,078) or TaxAC therapy (n = 2,052), Joanne Blum, MD, PhD, of the Texas Oncology-Baylor Charles A. Sammons Cancer Center, Dallas, reported at the annual meeting of the American Society of Clinical Oncology.
Patient and tumor characteristics were balanced among the two treatment arms, and the median follow-up time was 3.2 years.
Inferiority was predefined as a Cox model hazard ratio (HR) score of 1.18 or higher when the cohort was stratified by nodal status, hormone-receptor status, and parent trial, Dr. Blum said.
The HR for the initial 334 events was 1.2, which exceeded the threshold and demonstrated that TC was inferior to TaxAC.
At the interim analysis, 399 events had occurred: 220 in the TC treatment arm and 179 in the TaxAC arm. Overall, the 4-year invasive disease-free survival was 88.2% for the TC treatment arm and 90.7% for the TaxAC treatment arm (HR, 1.23; 95% confidence interval, 1.01-1.50; P = .04). TaxAC was equal or superior to TC when the cohort was stratified by parent trial, hormone status, and nodal status. TC regimen was favored only in ER-positive patients with zero nodes.
There was no difference in overall survival between the two treatment arms.
Exploratory subgroup analyses suggest that TaxAC provides little benefit in ER-positive, node-negative cohorts, small benefit in ER-positive one-to-three node and ER-negative node-negative cohorts, and the most benefit for patients who were ER-positive with more than four nodes or ER-negative node-positive, Dr. Blum said.
Acute leukemia occurred in 0.24% of patients in the TaxAC group and in none of the patients in the TC treatment arm.
“Additional follow-up and correlative studies to identify biomarkers of anthracycline benefit will be crucial for fully determining the utility of anthracyclines across this heterogeneous patient population,” Dr. Blum concluded.
Dr. Blum had no disclosures to report. Sanofi, Genentech, and CTEP funded the ABC trials.
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