An experimental breast cancer vaccine proved efficient in treating breast cancer caused by an excess of a protein called HER2 (Human Epidermal growth factor Receptor 2) according to a study by scietists at the School of Medicine and Karmanos Cancer Institute, Wayne State University, Detroid Michigan published in the American Association for Cancer Research’s journal Cancer Research.

Breast cancer represents about one quarter of all cancer cases. According to the American Cancer Society, the disease is the top cause of cancer death among women worldwide with an estimated 500,000 death annually. In the United States each year, more than 180,000 new breast cancer cases are diagnosed and more than 40,000 women die because of it.

About 20 to 30 percent of all breast cancer patients have the HER2 gene mutation. In cases of HER-2 positive metastatic breast cancer, tumors tend to grow faster and are more likely to recur than tumors that do not carry the protein.

There are drugs to treat this form of breast cancer. Herceptin made by Genentech Inc is one of these drugs but many patients become resistant to it and the tumors start growing again. Another therapy is Tykerb.

The new vaccine succeeded to eliminate tumors in mice with HER2 positive cancer even in those developing resistance to drugs designed to fight the disease. The new vaccine contains genes that produce the HER2 receptor and also a compound designed to stimulate the immune system.

“This may be the answer for women with these tumors who become resistant to the current therapies. This vaccine could potentially eliminate the need to even use these therapies,” principal investigator Dr Wei-Zen Wei, professor of immunology and microbiology at the Karmanos Cancer Institute, said.

Seeing the success of the vaccine, some scientists have suggested administering it to cancer-free woman as a preventive measure. It is known that women who test HER2 positive are genetically programmed to develop breast tumors.

Although the vaccine is seen as a breakthrough discovery, Dr. Sarah Rawlings, of the charity Breakthrough Breast Cancer said it is too early to declare the vaccine safe.

“This is very early research that has only been carried out in mice so we don’t actually know if it could be used in women. Much more research is neede to find out if it works, to either treat HER2 positive breast cancer or prevent the disease, and if there are any side effects.”

In April, the US military conducted a study on 163 patients whose tumors generated either low levels or high levels of HER2 protein. The women were injected with an experimental vaccine, called NeuVax, designed to trigger the immune system to fight breast cancer. After a 30 month-period, the injected vaccine was shown to cut the risk of death for all patients by half, and in the group of patients with low-expressing HER-2 tumors, no deaths were reported.