An experimental treatment shows promise for people with the most common form of advanced-stage breast cancer, according to results from a Phase 3 clinical trial.
The details of the trial were presented Thursday at the San Antonio Breast Cancer Symposium. It showed that AstraZeneca’s capivasertib – in combination with Faslodex (fulvestrant), an endocrine therapy already used to treat advanced breast cancer – gave people a median of 7.2 months without disease progression, compared with 3.6 months in people who got a placebo plus the endocrine therapy.
The trial involved 708 adults with HR-positive, HER2-low or -negative breast cancer whose disease has recurred or progressed during or after certain previous treatments.
About three-quarters of women with metastatic breast cancer have HR-positive breast cancer.
Capivasertib is an oral treatment given twice daily on an intermittent schedule: four days on and three days off. The drug blocks the activity of a cancer-driving protein molecule called AKT, according to the Institute for Cancer Research.
The finding on progression-free survival “was a substantial improvement,” said Dr. Harold Burstein, a physician at Dana Farber Cancer Institute and a professor of medicine at Harvard Medical School, who was not involved in the research.
“The good news is, looking at the data, it also seems to be a better-tolerated product than some of the drugs that already exist that target the same pathway.”
The findings are good, agreed Dr. Otis Brawley, a professor at the Johns Hopkins University Bloomberg School of Public Health and former chief medical officer of the American Cancer Society. But “progression-free survival” is a “wishy-washy, less-than-objective parameter,” he said.
“I see the reduction in risk of progression, but I do not see it saying reduction in risk of death,” said Brawley, who wasn’t involved in the study. That means more research will be needed to see whether the treatment lowers mortality risk, he said.
He points to the cancer drug Avastin, which was initially touted as having an advantage in progression-free survival for metastatic breast cancer.
“They forgot the other part of the trial, which is overall survival. Does it make people live longer? Does it cure people? Well, when that part of the study came in three years later, it turns out that Avastin made people live shorter,” Brawley said.
Although that may not be the case with capivasertib, he said, it is important to continue watching for the results of further trials.
Overall, scientists have made significant progress in treating breast cancer.
A study published in October found that in total, the death rate dropped 43% within three decades, from 1989 to 2020, translating to 460,000 fewer breast cancer deaths.
The capivasertib findings have not been peer-reviewed or published in a professional journal.
Burstein said he is encouraged by many of the presentations at the San Antonio Breast Cancer Symposium. With the positive results of research for breast cancer treatments, he thinks there will soon be a lot more choices, and he’s confident capivasertib will be one of them.
“That’s a good thing to have,” Burstein said. “More arrows in the quiver. That’s all very positive developments and very encouraging.”