Treatment Outcomes of Weakly Positive Hormone Receptor Breast Cancer and Triple-Negative Breast Cancer

Purpose: In breast cancer, response to endocrine therapy depends on estrogen receptor and progesterone receptor status. However, poor prognosis is conferred on patients with hormone receptor (HR)-positive breast cancer. We aimed to examine weakly positive HR breast cancer by comparing weakly positive HR to strongly positive HR and negative HR breast cancer. Methods: We examined the clinical and biological features of 1,496 women with breast cancer, and these patients were categorized according to HR status as weakly positive, strongly positive, and negative HR breast cancer. Results: In this study, among 1,496 patients with breast cancer, negative HR breast cancer was found in 374, weakly positive HR breast cancer in 90 and strongly positive HR breast cancer in 1,032 patients. Our multivariate analysis showed that there were differences in T stage, tumor–node–metastasis stage, vascular invasion, histologic grade and type, and Ki-67 index. Patients with weakly positive HR breast cancer had an increased risk of death and recurrence compared with those with strongly positive HR breast cancer and had similar prognosis as patients with negative HR breast cancer. Conclusion: Patients with weakly positive HR breast cancer received endocrine therapy because they were regarded as having positive HR breast cancer. However, their prognosis of overall survival and relapse-free survival was similar to that in patients with negative HR breast cancer. Therefore, we need to closely observe and consider active treatment for patients with weakly positive breast cancer.