A new research has revealed that a particular subtype of HER2-positive breast cancer tumor has displayed strong immune response to a single dose of the trastuzumab drug. The immune response was calculated by the researchers at Case Western University when they measured the immune activity within tumor tissue subsequent to giving the first dose of the drug.

When given a single dose of chemotherapy, no immune activity occurred in the HER2-positive patients. This reveals that the response of immune system to the drug is related to the particular substance and the tumor as well.

According to the National Cancer Institute, trastuzumab is available in the market under the name of Herceptin, which is used in the treatment of not only HER2-positive breast cancer, but also adenocarcinoma and metastasized cancer. The complete response towards trastuzumab drug before surgery is displayed in approximately 50% of women suffering from HER2-positive cancer. The percentage increases to 60% when other treatments are used along with trastuzumab.

The maximum immune response after a single dose was registered among women having an HER2-enriched subtype of HER2-positive breast cancer. The subtype is estrogen and progesterone receptor negative. The research was based on an earlier study that revealed that a tumor’s response towards treatment can be found by immune system. This paved way for clinical research to determine the immune system’s interaction with the drug.

“Our study showed, for the first time, that the immune-cell–activating properties of trastuzumab are likely related to the subtypes of breast cancer. Knowing this can inform future trials studying the usefulness of adding immunotherapy drugs to trastuzumab”, said Dr. Vinny Varadan, an Assistant Professor at Case Western Reserve University School of Medicine. The immune system’s response to the drug can be determined using the signatures of T-cell activity, by studying the increased expression of a marker of T-cells, known as PD-1.