Factors Determining Anthracycline Use in Hormone Receptor Positive, Early-Stage Breast Cancer

Anthracyclines are associated with significant toxicities whereas nonanthracyclines have proven to be better tolerated. A 21-gene assay allows clinicians to predict who will not benefit from adjuvant chemotherapy and avoid systemic toxicities. Physicians are using the recurrence score to guide chemotherapy selection, despite the lack of evidence. In this study we examined factors associated with prescribing patterns for an anthracycline-based chemotherapy in hormone receptor-positive stage I to III breast cancer.

This was a retrospective study using the Michigan Breast Oncology Quality Initiative data set (February 1, 2006 to December 31, 2015). Women with histologically confirmed stage I to III invasive breast cancer with estrogen receptor and/or progesterone receptor-positive, HER2/neu-negative receptor status were included. We used χ² analysis to determine associations of these characteristics with the 21-gene assay score and anthracycline use.

A total of 17,788 patients were evaluated. Most tumors were stage I (60%). Most procedures were lumpectomy with radiation (66%). Anthracyclines were used more often in stage III patients (69%), younger patients (40% for patients younger than 65 years), and those with higher 21-gene recurrence scores. Patients with low recurrence scores were more likely to receive anthracyclines if lymph node-positive (10%) than if lymph node-negative (1%; P < .001). Patients with high recurrence scores and lymph node-positive status were just as likely to receive an anthracycline-based as a nonanthracycline-based regimen (47.5% vs. 49.2%; P = .89).

These data indicate that medical oncologists might be anticipating the results of Adjuvant Chemotherapy Guided by a 21-Gene Expression Assay in Breast Cancer study (TAILORx) and the Clinical Outcomes in ER+HER2-node-positive Breast Cancer Patients Who Were Treated According to the Recurrence Score Results: Evidence From a Large Prospectively Designed Registry (RxPonder) trials and are avoiding the potential serious complications associated with anthracycline treatment in patients least likely to receive benefit.