Cancer researchers say the combination of a drug OK’d by regulators two years ago and older breast cancer meds significantly extended the lives of women who have an aggressive form of the disease, Reuters reports.

The drug is called Perjeta, and it is being used to help treat a type of breast cancer called HER2 positive, which makes up about a quarter of all diagnoses worldwide. Early reports showed that women taking Perjeta along with the older breast cancer drug Herceptin and courses of chemotherapy lived an average of almost 16 months longer than women on Herceptin and chemo alone.

“The survival improvement of nearly 16 months…is unprecedented among studies of metastatic breast cancer,” said lead researcher Sandra Swain, PhD, at the European Society for Medical Oncology’s annual Congress.

Researchers said this particular combination of medicines is so effective because the two drugs work together to bind to different parts of cancer-produced proteins in the body and sabotage their function.

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