Chemotherapy versus endocrine therapy as first-line treatment in patients with luminal-like HER2-negative metastatic breast cancer: A propensity score analysis

Background: According to current guidelines, endocrine therapy (ET) is recommended as first-line treatment of luminal-like metastatic breast cancer (MBC), whereas chemotherapy (CT) should be considered in presence of life-threatening disease. In daily practice, CT is often used outside of this clinical circumstance. Factors influencing first-line choice and the relative impact on outcome are unknown.

Methods: A consecutive series of luminal-like HER2-negative MBC patients treated from 2004 to 2014 was analyzed to test the association of disease- and patient-related factors with the choice of first-line treatment (ET vs. CT). A propensity score method was used to estimate impact of first-line strategy on outcome.

Results: Of 604 consecutive luminal-like MBC patients identified, 158 cases were excluded due to unknown or positive HER2-status. Among 446 HER2-negative cases, 171 (38%) received first-line CT. On multivariate analysis, the only factors significantly associated with lower CT use were old age (OR 0.25, 95%C.I. 0.13-0.49) or presence of bone metastases only (OR 0.26, 95%C.I. 0.13-0.53). In propensity score matched population, no differences were observed between CT and ET as first-line treatment either in terms of overall survival (37.5 months and 33.4 months respectively, log-rank test, P = 0.62) or progression-free survival (13.3 months and 9.9 months respectively, log-rank test, P = 0.92).

Conclusions: High percentage of patients with luminal-like MBC received CT as first-line therapy in real-life. The choice was mainly driven by age and site of metastases. With the limitations of a non-randomized comparison, no differences on patients' outcome were observed depending on the first-line strategy.