Reduction in risk of disease recurrence, the study's primary endpoint, was 51 percent in the ACTH study arm and 39 percent in the TCH arm.
"This is very promising news for the 250,000 women worldwide, including 50,000 in the United States, who will be diagnosed every year with this aggressive breast cancer," Slamon said.
The BCIRG study also resulted in two other important findings. Researchers knew that giving Herceptin with Adriamycin resulted in heart damage in some patients, the most severe of which was congestive heart failure. It was theorized, however, that this damage was not long lasting. But the BCIRG study showed the cardiac toxicity was significant and still persisted for more than 18 months at the date of the last follow up, Slamon said. This is vital information for doctors and patients to have when deciding which treatment regimen to use.
Of the 3,222 patients in the study, 353 experienced a greater than 10 percent loss of heart function. Of those, 91 patients (9 percent) were enrolled in the ACT study arm; 82 patients (8 percent) were in the TCH arm; and 180 patients (17.3 percent) were in the ACTH arm, which paired Adriamycin with Herceptin.
"We've always known that the major safety problem with Herceptin has been cardiac toxicity when it is used with Adriamycin," Slamon said. "When breast cancer patients lose their hair, it grows back. When we suppress their bone marrow, that comes back, too. Heart failure, however, is a much larger problem, especially if it does not improve over time."