Effect of Hormone Therapy on Long-term Outcomes of Patients with Human Epidermal Growth Factor Receptor 2- and Hormone Receptor-Positive Metastatic Breast Cancer: Real World Experience in China

Background: Among human epidermal growth factor receptor 2 (HER2)-positive breast cancer, more thanhalf are also hormone receptor (HR)-positive. Although HR is a predictive factor for the efficacy of hormonetherapy, there are still some uncertainties in regard to the effects on patients with HR-positive and HER2-positivemetastatic breast cancers due to the potential resistance to hormone therapy caused by co-expression of HRand HER2. There are no clinical trials directly comparing the efficacy of hormonal therapy with chemotherapy.Materials and
Methods: To examine the real-world effect of hormone therapy on patients with HR-positiveand HER2-positive metastatic breast cancers, a cross-sectional study of a representative sample of the Chinesepopulation was conducted. The study included 113 patients who received first-line and second-line palliativetreatment between 2005 and 2010 in the Cancer Institute and Hospital, Chinese Academy of Medical Science.The effect of hormone therapy on overall survival (OS) was studied.
Results: The patients who received hormonetherapy (n=51) had better overall survival in contrast to those who received chemotherapy with anti-HER2therapy (n=62) in first- or second-line treatment. The difference was of borderline statistical significance (51.8mvs 31.9m, p=0.065). In addition, the effect of hormone therapy did not differ significantly with other prognosticfactors, including age (≤50 years or >50 years), disease free survival (≥2 years or < 2 years) and site of metastasis(visceral or bone/soft tissue). On multivariate analysis, administration of hormone therapy was associated witha trend toward a favorable prognosis (p=0.148, HR=0.693, 95%CI 0.422-1.139). Age more than 50 years wasthe sole independent harmful prognostic factor (p<0.001, HR=2.797, 95%CI 1.676-4.668).
Conclusions: Ourdata suggest that hormonel therapy may improve outcomes of the patients with ER-positive and HER2-positivemetastatic breast cancer.