Adjuvant endocrine therapy alone in patients with node-positive, luminal A type breast cancer

Luminal A breast cancer has a much better prognosis than other subtypes, with a low risk of local or regional recurrence. However, there is controversy around under- versus overtreatment with regard to adjuvant treatment of node-positive, luminal A breast cancer. The purpose of this study was to identify whether adjuvant systemic chemotherapy has any benefit in node-positive, luminal A breast cancer and to evaluate feasibility of endocrine therapy without chemotherapy in this group. This was a retrospective study of 11,025 patients who were surgically treated for invasive breast cancer at Samsung Medical Center between January 2004 and December 2013. Luminal A subtype was defined as ER+, HER2-, and Ki-67 < 14%. We compared AC based (AC: doxorubicin or epirubicin, plus cyclophosphamide) adjuvant chemotherapy versus endocrine therapy without chemotherapy in patients with node-positive, luminal A breast cancer. We performed 1: n matching, with a maximum n of 8 on endocrine therapy group (n = 50) to chemotherapy group (n = 642). The median age of the patients in each group at the time of surgery was 58.3 ± 9.5 years in the chemotherapy group and 58.7 ± 11.7 in the endocrine therapy only group. The median follow-up time was 51.9 months (range, 1–125 months). In multivariable analysis, omission of adjuvant chemotherapy in luminal A cancer had no influence on OS and DFS. Axillary lymph node metastasis and progesterone receptor (PR) status were significantly different between the endocrine therapy alone group and the chemotherapy group in terms of OS. Nuclear grade, PR status, and adjuvant radiotherapy were significantly different between the endocrine therapy alone group and the chemotherapy group with regard to DFS. In survival analysis, there were no differences in OS (P = .137) and DFS (P = .225) between the 2 groups. Adjuvant chemotherapy could provide little benefit to postmenopausal patients with luminal A, node-positive breast cancer, and endocrine therapy alone may help reduce morbidity. Future studies with a large number of patients and longer follow-up time are necessary to determine whether chemotherapy might be avoided in this patient population.