Breast Cancer Drug Aromasin May Be Option for Some
It produced lower 5-year recurrence rates compared to tamoxifen, but didn't boost overall survival, study finds
By Kathleen Doheny
WEDNESDAY, July 9, 2014 (HealthDay News) -- The drug exemestane worked slightly better than the drug tamoxifen at preventing a recurrence of breast cancer in certain premenopausal women, according to a new study.
Almost 93 percent of women on exemestane (Aromasin) remained free of breast cancer after five years, compared to about 89 percent of the women on tamoxifen. That's according to the study of nearly 4,700 women with breast cancer who all had their ovarian function suppressed.
However, the researchers found no differences in overall survival between the two drugs.
And both drugs came with significant side effects. For Aromasin, those side effects included osteoporosis, vaginal dryness and decreased sex drive, among others. For tamoxifen, side effects included blood clots, hot flashes and urinary incontinence, according to the study.
The study is published in the July 10 issue of the New England Journal of Medicine. The findings were also presented at the American Society of Clinical Oncology annual meeting in June.
Some breast cancers -- dubbed hormone receptor-positive -- are fueled by the hormone estrogen. Tamoxifen works by blocking estrogen from getting into cancer cells. Aromasin -- part of a class of drugs known as aromatase inhibitors -- works by stopping other hormones from changing into estrogen, according to the American Cancer Society. Aromatase inhibitors are only helpful if the ovaries aren't still producing estrogen.
That's why aromatase inhibitors have traditionally been used in postmenopausal women, and have been shown to work better for them than tamoxifen. Tamoxifen is typically used in breast cancer patients who have not yet gone through menopause because it can block estrogen that's circulating in the body.
Now, the new study suggests that aromatase inhibitors may be an option for premenopausal women, although not everyone thinks the new research will greatly change practice.
"It's another option," said Dr. Joanne Mortimer, director of women's cancer programs at the City of Hope Comprehensive Cancer Center in Duarte, Calif. She reviewed the findings and said that the aromatase inhibitor would be a trade-off. "Compared to aromatase inhibitors, the quality of life is better with tamoxifen for premenopausal women," she said.
The study was funded by the U.S. National Cancer Institute, Pfizer (which makes Aromasin), Ipsen (makers of an ovarian suppression drug) and the International Breast Cancer Study Group.
The study researchers combined the results of two phase 3 clinical trials, known as the Tamoxifen and Exemestane Trial (TEXT) and the Suppression of Ovarian Function Trial (SOFT).
All of the women in the studies had hormone receptor-positive breast cancer. They also all had their ovarian function suppressed to further thwart cancer growth.
Both studies included analysis of five years of treatment over a median follow-up of more than 5.5 years.