Strong immune response can signal aggressive breast cancer – new Finnish study helps identify high-risk patients and target treatments more precisely

Combining biomarkers for tumorous immune response and cell proliferation makes it possible to predict the trajectory of advanced breast cancer with greater accuracy than before, according to a study from the University of Oulu that has gained international attention. Researchers tracked 398 Finnish patients with advanced breast cancer to understand why some benefit from treatment while others experience rapid disease progression despite modern therapies.

A robust immune reaction does not always mean treatment is working

The researchers were surprised to find that immune system activity does not mean the same thing across all breast cancer subtypes; rather, the significance of the immune response depends heavily on the specific subtype. In particularly aggressive triple-negative breast cancer, a high abundance of immune cells was associated with a better prognosis, whereas in hormone receptor-positive, HER2-negative disease, the finding was the exact opposite.

“This highlights that the immunobiology of breast cancer is significantly more complex than previously thought. The results challenge the simplistic view that a strong immune response is always a positive sign,” says researcher Sauli Vuoti from the University of Oulu.

The patients' tumours were analysed for both immune response and several biomarkers indicating cell proliferation activity. The findings were then compared with treatment responses, disease progression, and overall survival rates.

Tumour-infiltrating immune cells and several cell-division biomarkers were found to be particularly strongly linked to prognosis. Among these, MCM2, a marker reflecting cell proliferation activity, proved to be an exceptionally powerful indicator of the risk of disease recurrence and progression.

Towards truly personalized breast cancer care with a biomarker panel

This is one of the most comprehensive Finnish breast cancer datasets in which the combined effects of several well-known biomarkers have been analysed side by side. The new study demonstrates for the first time how combining these markers can create a practical tool for identifying both the specific type and aggressiveness of breast cancer.

The method has already been implemented in several Finnish hospitals, and international testing is currently underway.

“A biomarker panel like this helps clinicians identify patients who will benefit most from targeted therapies or intensified treatment protocols. By identifying high-risk patients early, healthcare resources can be allocated more effectively. This reduces healthcare costs and alleviates human suffering. Thus, our research supports the objectives of the Finnish Cancer Strategy regarding treatment efficacy and personalized cancer medicine,” Vuoti explains.

The study was funded by the Jenny and Antti Wihuri Foundation and the Jane and Aatos Erkko Foundation. The findings have been published in the international scientific journal Breast Cancer Research and Treatment:

Vuoti, S., Saari, M., Lahti, J. et al. Association of baseline tumor-infiltrating lymphocytes and cell-cycle regulation markers on prognosis and mortality in patients with advanced breast cancer according to tumor characteristics and treatment type: an observational study. Breast Cancer Res Treat 217, 41 (2026). https://doi.org/10.1007/s10549-026-07991-9