Factors influencing the development of visceral metastasis of breast cancer: A retrospective multi-center study.

PURPOSE: Visceral metastasis of breast cancer (BC) is an alarming development and correlates with poor median overall survival. The purpose of this retrospective study is to examine the risk factors for developing visceral metastasis by considering tumor biology and patient characteristics. METHODS: Using the BRENDA database, the risk factors such as histological and intrinsic subtypes of BC, age at primary diagnosis, grading, nodal status, tumor size and year of primary diagnosis were examined in univariate and multivariate analysis. Categorical variables were compared by using χ2 tests. Furthermore, multivariate Cox proportional hazards regression models, Kaplan-Meier product-limit method and log-rank test were applied. The results of two tree-building algorithms, "exhausted CHAID" (Chi-squared Automatic Interaction Detector) and CART (Classification and Regression Trees) were verified with further multivariate analysis, radial basis function networks (RBF-net), feedforward multilayer perceptron networks (MLP) and logistic regression. RESULTS: In a patient collective of 886 metastasized patients, 56.9% had developed visceral metastases and 27.1% visceral-only metastases. The different histological and intrinsic subtypes of BC and the grading correlate significantly with the visceral-only metastasis behavior, whereas the age at primary diagnosis, the nodal status, the tumor size and the year of the primary diagnosis had no influence. Patients with ductal/other BC, LuminalB/HER2, TNBC, HER2 overexpressing subtype and grade 3 had an increased risk for the development of visceral-only metastasis. CONCLUSIONS: Intrinsic and histological subtypes as well as the grading of BC affected significantly the visceral metastasis behavior.