Metastatic Breast Cancer: Is There a Differential Therapy Efficacy between Visceral and Non-Visceral Metastatic Breast Cancer?

Purpose:Differential efficacy of newly registered therapies in subgroups of metastatic breast cancer (MBC) is an important consideration for subsequent use in clinical practice. Unfortunately, such subgroup analyses often are exploratory and rarely statistically adequately powered and may thus be misleading. This analysis aimed to explore a potentially different treatment response to i.v. therapies between visceral and non-visceral MBC.Methods:In a systematic literature analysis (PubMed) comprising phase III registration studies for MBC from 1994 to 2014, differences in outcome were evaluated regarding progression-free survival, time to progression, overall survival (OS), and visceral versus non-visceral disease. The impact of HER2 and hormone receptor status was also considered. A total of 16 studies comprising 13,083 patients were selected by considering the information given in the medical product's professional information and the decision of the US Food and Drug Administration or the European Medicine Agency for approval of the respective therapeutic agents now used in the treatment of MBC.Results:No statistically significant differences regarding treatment response and therapy benefit were found in MBC patients with visceral versus non-visceral metastases based on reported hazard ratios and confidence intervals in registration trials. Interesting but nonsignificant differences were found regarding a distinct therapy benefit regarding different metastasis locations in 4 studies.Conclusion:For targeted i.v. therapies based on biomarker selection, there is a trend - although not significant - toward a benefit (OS) from combination therapies favoring visceral disease. However, at the present time, metastasis localization should not be used as a predictive marker for choice of systemic therapy in MBC.