WEDNESDAY, Dec. 5, 2018 (HealthDay News) -- For certain women with early stage breast cancer, a newer drug that combines an antibody with chemotherapy may cut the risk of disease recurrence in half, a new trial finds.
The study focused on nearly 1,500 women with early stage breast cancer that was HER2-positive -- meaning it carries a protein that promotes cancer growth.
About one in every five breast cancers is HER2-positive.
All of the women in the new trial had undergone a standard treatment scenario. First, they received traditional chemotherapy and the drug Herceptin (trastuzumab) -- an antibody that targets HER2-positive cancer cells. Then they had surgery to remove any remaining cancer.
Often, women find out that the chemo-Herceptin therapy has already wiped out the cancer, explained Dr. Charles Geyer, the lead researcher on the new study.
But for many other women, there is still "residual" cancer at the time of surgery. And they have a relatively higher risk of seeing their cancer come back, said Geyer, a professor of medicine at Virginia Commonwealth University in Richmond.
All of the women in his study fell into that category.
Right now, the standard of care is to keep those patients on Herceptin for another year after surgery. Geyer's team wanted to know if women might fare better on a different drug, Kadcyla.
Kadcyla is a newer drug that combines Herceptin with a chemotherapy drug called emtansine. In the United States, it's approved by the Food and Drug Administration for treating some women with advanced HER2-positive breast cancer.
Geyer explained the basics of how the drug works: "The chemotherapy is attached to the antibody. The idea is that the antibody will carry the chemo directly into the cells that you want to hit."
Geyer and his colleagues reasoned that Kadcyla might be more effective than Herceptin at preventing recurrences in their early stage patients.
"It turned out that hypothesis was correct," he said.
Of women who received the drug for a year after surgery, 88 percent were alive and cancer-free three years later. That compared with 77 percent of those given Herceptin.
"That difference is quite substantial," said Dr. Eric Winer, a medical oncologist at Dana-Farber Cancer Institute in Boston.
Winer, who was not involved in the research, said the findings will probably "change practice in the short term."
Kadcyla is not yet approved to treat patients like those in this trial. But doctors are free to use FDA-approved drugs for reasons other than their official indication -- though insurers have to agree to pay.
Winer said that with this new evidence, "it's likely" insurers will pay for Kadcyla in cases like these.
When it was approved in 2013, the drug's cost was more than $90,000 for a typical course of treatment -- about double the price of Herceptin.
Geyer was scheduled to present the findings Wednesday at the annual San Antonio Breast Cancer Symposium. The study was published simultaneously online in the New England Journal of Medicine.
The research was funded by Kadcyla maker F. Hoffmann La Roche/Genentech. Geyer is an unpaid member of the company's breast cancer advisory boards.
The study involved 1,486 women with early stage cancer who still had tumor tissue left after standard chemotherapy and Herceptin. Following surgery, they were randomly assigned to receive either Kadcyla or Herceptin for about a year. Both drugs are given by infusion, every three weeks.
The women were followed for three years after their treatment. At that point, about 12 percent of Kadcyla patients had suffered a recurrence or died, versus 22 percent of Herceptin patients.
However, there were more side effects with Kadcyla, Geyer said. They included a drop in blood platelets -- cells that help the blood clot -- plus nerve symptoms such as numbness, and elevations in liver enzymes.
But the majority, according to Geyer, were at the milder "grade 1 or 2" level.
Winer framed the findings within a bigger picture: Over the past two decades, treatment advances -- including Herceptin and similar drugs -- have allowed more and more women with HER2-positive breast cancer to fare well.
"This study is another step in the direction of preventing more recurrences," he said. "It's exciting."
Geyer agreed. "Women with HER2-positive cancer generally have a very favorable outlook," he said. "The group having recurrences is getting smaller and smaller."
The American Cancer Society has more on HER2-positive breast cancer.