An experimental drug keeps a certain kind of aggressive breast cancer at bay, say researchers.
The phase III trial comparing trastuzumab emtansine (T-DM1) to standard therapy for human epidermal growth factor receptor 2 (HER2 positive) breast cancer was presented at the American Society of Clinical Oncology conference in Chicago.
The international study randomized nearly 1,000 patients to receive either T-DM1 or standard therapy every three weeks. The subjects all had metastatic cancer that had spread to other parts of the body.
The trial found that progression-free survival in the T-DM1 group was 9.6 months, compared to 6.4 months in the standard therapy group, which study authors described as "clinically meaningful improvement."
"The drug worked. It was significantly better than a very effective approved therapy for HER2 overexpressing metastatic breast cancer," said lead study author Kimberly Blackwell, professor of medicine at Duke University.
"Also, as a clinician who takes care of a lot of breast cancer patients, I'm pleased that this drug has very little dose-limiting toxicity. Patients don't lose their hair from this drug.
"For patients facing metastatic breast cancer, this is a breakthrough."
The data on overall survival time showed 65 percent of T-DM1 patients were alive after two years, compared to 47.5 percent of the standard therapy patients, a threshold that fell short of the trial's predetermined limits for judging statistical significance.
More analysis of survival times is planned for later in the ongoing study.