Predicting the site of distant metastases in breast cancer

Background. Distant organ tumor dissemination is a major cause of breast cancer-related deaths. Breast cancer can metastasize to several organs, and the most frequent metastatic sites include the bones, lungs and liver. There is a question what factors can influence the direction of spread of tumor cells to a particular organ. Material and Methods. We summarized the data available in the world literature on methods for prediction of the localization of distant metastases in breast cancer patients. Results. We divided the factors associated with the localization of distant metastases into two main groups: clinicopathological parameters of breast cancer patients and molecular features of tumor microenvironment and tumor cells (primary tumor and circulating tumor cells) or its derivates – exosomes. From our point of view, the most powerful clinicopathological factor predicting the distant metastasis site is a molecular subtype of primary tumor. We can conclude that luminal (HR+/HER2-) tumors are often characterized by single metastases and bones are the most common metastatic site, while TNBC and HER2-enriched tumors often metastasize to multiple sites, most commonly brain and liver. However, several authors did not reveal these associations in their studies. It likely indicates the existence of other factors that significantly affect the organotropism of metastasis. Numerous studies demonstrate the association of different molecules expressed on tumor cells with organotropic metastasis. However, these data are very fragmentary and rather contradictory. Conclusion. The found associations are common to all participants of metastatic cascade, but remains unclear which factors are essential and crucial in determining the direction of metastasis.