New Treatment for Young Breast Cancer Survivors
Drug appears more effective than tamoxifen at reducing recurrence in premenopausal women: study
By Dennis Thompson
SUNDAY, June 1, 2014 (HealthDay News) -- A new type of anti-estrogen drug appears to work better than the estrogen-blocking drug tamoxifen in preventing recurrences of breast cancer in certain women, a new study reports.
Exemestane (Aromasin), which belongs to a class of drugs called aromatase inhibitors, reduced the relative risk of breast cancer recurrence by nearly a third compared to tamoxifen. But, for exemestane to work in premenopausal women, the drug can only be given when ovarian function is being suppressed.
"For years, tamoxifen has been the standard hormone therapy for preventing breast cancer recurrences in young women with hormone-sensitive disease. These results confirm that exemestane with ovarian function suppression constitutes a valid alternative," study lead author Dr. Olivia Pagani, clinical director of the Breast Unit at the Oncology Institute of Southern Switzerland in Bellinzona, Switzerland, said in a prepared statement.
Findings from the study were scheduled to be presented Sunday at the American Society of Clinical Oncology (ASCO) annual meeting in Chicago. The study was also published simultaneously in the New England Journal of Medicine. Funding for the study was provided by drug makers Pfizer and Ipsen, as well as the International Breast Cancer Study Group and the U.S. National Cancer Institute.
Aromatase inhibitors, such as exemestane, work by preventing other hormones from changing into estrogen, which is the female hormone that often fuels breast cancer growth.
By comparison, tamoxifen blocks estrogen from being used by cancer cells.
Tamoxifen has been the default standard of care for premenopausal women because aromatase inhibitors are not effective in women whose ovaries are functioning, said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society.
"The amount of estrogen in their bodies is too great for it to have a beneficial function," Lichtenfeld said.
But doctors wondered whether aromatase inhibitors could be used to better protect young women against breast cancer if their ovary function was suppressed, essentially putting them through menopause and reducing their estrogen levels.
This study analyzed treatment outcomes of almost 4,700 breast cancer survivors who participated in two worldwide clinical trials aimed at answering that question.
The women, average age 43, all underwent treatment to stop their ovaries from functioning. Each chose one of three methods, Lichtenfeld said -- they could take medication to suppress ovary function, have their ovaries exposed to radiation, or have their ovaries surgically removed.
On top of ovary suppression, the women were randomly assigned to take either exemestane or tamoxifen to help prevent a recurrence of their breast cancer.
The cancer-free survival rate at five years ended up 91.1 percent in the exemestane group versus 87.3 percent in the tamoxifen group. That amounts to a 28 percent lower risk of subsequent invasive cancer, the researchers reported.