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.