Intra-mammary tumor location does not influence prognosis but influences the prevalence of axillary lymph-node metastases

The number of axillary lymph-node metastases is not only a function of disease progression in primary breast cancer, but is also influenced by the intra-mammary location of the tumor. Nevertheless, the prognostic role of the tumor site is discussed controversially. The objective of this study was to analyze the impact of primary-tumor location on axillary lymph-node involvement, relapse, and mortality risk by univariate and multivariate analysis, in patients both with and without systemic and loco-regional treatment.

Retrospective analysis was conducted on 2,414 patients at the I. Frauenklinik, Ludwig-Maximilians University, Munich and Berlin-Charlottenburg, who underwent R₀ resection of the primary tumor and systematic axillary lymph-node dissection (at least five lymph nodes resected) for UICC I-III-stage breast cancer. Patients with unknown tumor site, multifocal tumor spread, central tumor location, or tumor location within 15° of the border between outer and inner quadrants were excluded from the study. Median observation time was 6.7 years.

The primary tumor site was within or between the medial quadrants of the breast in 33.6% of the patients (n=810) and in the lateral hemisphere of the breast in 66.4% (n=1,604). Tumor size, histopathological grading, and estrogen receptor status were balanced between patients with lateral and medial tumor location. Metastatic axillary lymph-node involvement was significantly associated with a lateral tumor location (P<0.0001). The mean number of axillary lymph-node metastases was increased by 29% in cases with lateral tumor location (2.2 vs 1.7, P=0.003). In a multivariate logistic regression analysis allowing for tumor location, estrogen receptor status, grading and tumor size, tumor location was confirmed as a significant risk factor (P=0.02) for axillary lymph-node involvement. Tumor location, however, did not correlate with either disease-free survival (DFS) or overall survival (OS), by univariate (DFS: P=0.41; OS: P=0.57) or by multivariate analysis (DFS: P=0.16; OS: P=0.98).

We conclude that there is no sufficient evidence to support any independent prognostic significance of intra-mammary tumor location in early breast cancer. However, medial tumor location may lead to the underestimation of axillary lymph-node involvement.