Triple negative breast cancer is one of the most difficult types of cancer to treat. It lacks proteins that can attract powerful anti-cancer and hormone drugs, so people diagnosed with the disease have to rely almost exclusively on chemotherapy.

But in a new presentation at the annual American Association for Cancer Research meeting, researchers say that one of the latest immunotherapy drugs called atezolizumab, or Tecentriq, may help people with triple negative breast cancer to live longer.

The study, which involved women with triple negative breast cancer that had spread, did not compare people taking atezolizumab to a placebo. Rather, it looked at who responded to the drug versus who did not. All of the responders among the 112 people in the study were alive after one year, compared to 38% of those who did not respond to the drug.

“This is a group of patients who are benefiting from something we couldn’t offer them a few years ago,” says Dr. Peter Schmid, professor of cancer medicine and director of the breast center at St. Bartholomew’s Breast Centre in London.

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Atezolizumab is an antibody that releases the brakes that the immune system puts on destroying tumor cells, which start from normal cells but grow out of control. Schmid and his colleagues found that the drug can control growth and spread of triple negative breast cancers, and the earlier women receive the treatment, the better they fare. Among those who took the drug as their first-line therapy, 26% responded. Only 10% did if they had tried some other treatments first. “It’s not where we would like it to be, but it’s a very strong signal,” says Schmid.

Schmid says that he and his colleagues are working on finding ways to know which people will respond to drugs like atezolizumab and which people won’t. They’re also investigating combinations of drugs and pairing the drug with chemotherapy, tactics that may improve survival even more. They’re hopeful that better treatments are coming. “This is the most encouraging signal I’ve seen in metastatic triple negative breast cancer,” he says.

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