Pfizer's new targeted drug, palbociclib, has been shown to halt the progression of the most common form of advanced breast cancer in women, researchers said Saturday.
The phase III trial was stopped early after it became clear that the drug—when taken in combination with the anti-estrogen treatment Fulvestrant—was doubling the amount of time the cancer could be kept in check.
The combination delayed disease progression by just over nine months—compared to nearly four months in women taking Fulvestrant alone—for those suffering from a kind of advanced breast cancer known as hormone receptor-positive, human epidermal growth factor receptor 2 negative (HR+/HER2-), which account for about three quarters of all breast cancers.
The randomized study involving 521 women, 79 percent of whom were post-menopausal, was presented at the American Society of Clinical Oncology (ASCO) annual conference in Chicago.
"After initial hormonal therapy stops working in metastatic breast cancer, the next step is typically chemotherapy, which can be effective, but the side effects are often very difficult for women," said lead study author Nicholas C. Turner, a consultant medical oncologist at The Royal Marsden and a team leader at The Institute of Cancer Research, London, United Kingdom.
"This relatively easy-to-take new drug can substantially delay the point when women need to start chemotherapy, making this an exciting new approach for women."
Palbociclib works by blocking a key protein that fuels the growth of hormone receptor-positive breast tumors.
Researchers said that comparable benefits were seen in both pre- and postmenopausal women, but more long term research is needed to determine whether or not the drug helps women live longer.
Commenting on the study, ASCO expert Don Dizon of Massachusetts General Hospital, said the combination treatment appeared to work as well in older women as it did in younger women.
"For women with advanced breast cancer, it's remarkable to be able to stall disease progression and stave off the need for chemotherapy for months with a simple pill," he said.
The US Food and Drug Administration has granted palbociclib accelerated approval for use in combination with another drug, letrozole (Femara), for women with advanced estrogen receptor positive (ER+), HER2- breast cancer who have not yet received hormonal therapy.
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