Prognostic Implication of the Primary Tumor Location in Early-stage Breast Cancer: Focus on Lower Inner Zone

Background: The aim of this study was to investigate the prognostic significance of tumor location of lower inner zone (LIZ) on the survival of patients with early-stage breast cancer.

Methods: We retrospectively identified 961 breast cancer patients from Jan 2000 to Apr 2016 from hospital database. We evaluated overall survival (OS) and disease-free survival (DFS) in patients with tumors in and outside LIZ. Subgroup analyses were performed according to clinicopathological characteristics and treatment strategies.

Results: A total of 838 cases were finally included. Patients with tumor location of LIZ showed significantly lower survival rates than tumors in other sites in terms of DFS (p = 0.028) but not OS (p = 0.106). When stratified into subgroups, tumors in LIZ retained a significant worse prognosis in DFS in patients with HER-2-negative, high ki-67 expression breast cancers, those who received neoadjuvant chemotherapy, axillary nodal negative patients, and patients with lymphovascular invasion. Univariate and multivariate analyses suggested that tumor location of LIZ was an independent prognostic factor for DFS (p = 0.022).

Conclusions: Our results suggested that tumor location of LIZ was an independent adverse prognostic factor for DFS in patients with early-stage breast cancer. Multicenter studies with larger sample size are needed to confirm the conclusion and anatomical experiments are desired to elaborate the mechanism.