Linda Lindström

Breast cancer is a very heterogeneous disease with different ability to spread and time to possible spread. Of the women who develop breast cancer, about one in four women will die. Most women are diagnosed with hormone-sensitive cancer, which means that the tumor is dependent on estrogen to grow, but only 50% of women benefit from hormonal treatment. Different tumor characteristics (breast cancer markers) determine what treatment a woman should receive. However, these do not predict patients' long-term risk of dying from their disease. Which is important to realize as breast cancer is common in mid-life and carries a risk of many lost female years. We have shown that patients who have tumor cells with different expressions, ie intra-tumor heterogeneity of estrogen (a breast cancer marker) within their tumor have twice the risk of dying from breast cancer. Our aim is therefore to investigate whether intra-tumor heterogeneity of the clinically used breast cancer markers and other tumor characteristics affect a patient's risk of dying from breast cancer. This is done by uniquely comparing intra-tumor heterogeneity of tumor properties (at the protein level and gene level) in women who have died of their disease and women who have survived in a unique way in large clinical cancer studies with long follow-up and detailed information. Our project aims to provide increased knowledge about factors that affect survival by identifying tumor characteristics that predict which patients have a high risk of dying from their disease and patients who do not benefit from hormonal treatment. Given that the markers are analyzed in large randomized studies and in close interdisciplinary collaboration with pathologists and oncologists, the knowledge, if it proves interesting, should be able to be used in the near future. This can be of great importance for women with breast cancer, and provide the opportunity for customized treatments and controls for women with a high risk of late recurrence of the disease.