Biomarker can be breast cancer response to immunotherapy

A biomarker that has proven to be a predictor for response to immunotherapies in melanoma patients also has clinical relevance for breast cancer patients, according to a new study led by Vanderbilt University Medical Center.

The findings of the study were published in Clinical Cancer Research, a journal of the American Association for Cancer Research.

The study demonstrated that this biomarker, a molecule called the Major Histocompatibility Complex Class II protein (MHC-II), has the potential to be a predictor of immunotherapy benefit with two types of breast cancer- early-stage, triple-negative breast cancer (TNBC) and high-risk, estrogen receptor-positive breast cancer (HR ) when expressed on breast cancer cells.

Although immunotherapies are likely to soon be prescribed along with chemotherapies for these breast cancers before surgery, most patients don't require the addition of immunotherapy to achieve treatment response. Without an optimal biomarker, clinicians don't have a reliable way to discern which patients need immunotherapy and which ones don't.

Clinical tests for MHC-II expression could shield breast cancer patients who don't need the immunotherapy from possible treatment complications and additional costs. Immunotherapies are expensive and associated with significant toxicity.

Justin Balko, PharmD, PhD, associate professor of Medicine and Pathology, Microbiology and Immunology, conceived and designed the study.

"These findings are particularly exciting for us because if validated, they could provide a better way to personalize therapy for breast cancer patients. So far, the typical biomarkers like PD-L1 expression and the numbers of immune cells in the tumour have not done a good job of identifying patients who need immunotherapy," said Balko, the study's senior author.

Paula Gonzalez Ericsson, the study lead author, added, "the test can be easily performed on patient's tissue samples obtained for diagnosis without the need of additional intervention."