Researchers: Future therapies for aggressive breast cancer can be more effective and much less toxic

A combination of two existing cancer drugs for treating HER2-positive metastatic cancer, an aggressive form of breast cancer, performed better and were less toxic than standard therapies, according to researcher Edith Perez, MD, of the Mayo Clinic in Florida.

T-DM1, combines trastuzumab, an antibody that targets cells that overproduce the HER2 protein; and DM1, a chemotherapy drug that targets microtubules. 

In the trial, 137 women with HER2-positive metastatic cancer were randomly assigned to receive treatment with either T-DM1 or trastuzumab combined with docetaxel, another chemotherapy drug. None of the patients had received any type of chemotherapy for their metastatic cancer before joining the study.

After six months, 48 percent of the patients who were given T-DM1 had a reduction in tumor size and growth, compared with 41 percent in the trastuzumab plus docetaxel group. The women who received T-DM1 had fewer toxic side effects from the treatment than did those who received traztuzumab with docetaxel, 37 percent versus 75 percent.

Daily broadcasts and news articles from the European Society for Medical Oncology (ESMO) Congress, October 8-12.Fabrice André, MD, Institut Gustave Roussy in Villejuif, France, said the trial showed that it’s possible to develop chemotherapy that are both effective and less toxic than current standard therapies.

“The rates of serious adverse events were much lower in patients given T-DM1 compared to the chemotherapy arm,” said André. “These results suggest that, with the same efficacy, T-DM1 could dramatically reduce the toxicities related to chemotherapy.”

André also said the study proved a concept: that linking a monoclonal antibody to a cytotoxic drug leads to an anticancer effect. “This could have several implications beyond drugs that target HER2,” André said.

Perez presented the results of the  trastuzumab-DM1 (T-DM1) trial on the opening day of the European Society for Medical Oncology meeting in Milan, Italy. The conference runs through October 12.

A larger study of T-DM1 and other cancer drug combinations is already underway. This trial, called the MARIANNE study, evaluates taxane plus trastuzumab, compares  taxane plus trastuzumab to T-DM1, and also evaluates the effectiveness and toxicity of T-DM1 with pertuzumab, another anti-HER2 agent, said Perez.