Clinical pattern of primary systemic therapy and outcomes of estrogen receptor-positive, HER2-negative metastatic breast cancer: a review of a single institution.

PURPOSE: In the management of estrogen receptor-positive, human epidermal growth factor receptor 2-negative metastatic breast cancer (ER+HER2-MBC) patients, endocrine therapy (ET) is preferred to chemotherapy (CT) as a primary systemic therapy (PST) when tumor burden is not high. However, there are no definite criteria for choosing a PST, transitioning from ET to CT or using maintenance ET subsequent to CT.
METHODS: We reviewed the medical records of 311 ER+HER2-MBC patients who underwent CT from September 2002 to December 2016 and assessed their outcomes.
RESULTS: Of the 311 patients, 178 (57%) received ET as a PST (ET-first group), and 133 (43%) received CT prior to ET (CT-first group). The ET-first group showed a median overall survival (OS) from the diagnosis of MBC (OSMBC) of 1593 days, and the median OS from the initiation of CT (OSCT) was 938 days. Patients with visceral involvement, liver metastasis, soft tissue metastasis, ≥3 organ involvement, or primary advanced BC at the MBC diagnosis showed a significantly higher tendency to be assigned to the CT-first group (P < 0.01 for any visceral involvement, P < 0.05 for all others). Maintenance ET was available in 74 (55.6%) patients in the CT-first group, who showed a significantly better OSMBC and OSCT than patients without maintenance ET (median OSMBC 1423 and 867 days, respectively, P < 0.0001; median OSCT 1350 and 637 days, respectively, P < 0.0001).
CONCLUSION: Our findings suggest the possibility for changing the treatment paradigm of patients with ER+HER2-MBC, so a randomized prospective study is warranted to determine the optimum sequence of systemic therapies.