SOURCES: Prudence Francis, M.D., head, breast medical oncology, Peter MacCallum Cancer Centre, Melbourne, Australia; George Somlo, M.D., professor, medical oncology, City of Hope Cancer Center, Duarte, Calif.; Dec. 11, 2014, San Antonio Breast Cancer Symposium; Dec. 11, 2014, New England Journal of Medicine
THURSDAY, Dec. 11, 2014 (HealthDay News) -- A treatment known as ovarian suppression used along with an anti-estrogen drug normally given to older women appears to greatly reduce the risk of breast cancer recurrence in some younger women, new research suggests.
This combination approach -- using estrogen-blockers known as aromatase inhibitors -- was the most effective of three treatments tested in women with early stage breast cancer, said Dr. Prudence Francis, head of breast medical oncology at the Peter MacCallum Cancer Centre in Victoria, Australia.
She is scheduled to present her findings Thursday at a breast cancer meeting in San Antonio. The results will be published online simultaneously in the New England Journal of Medicine.
Hormone receptor-positive breast cancer -- the most common type of breast cancer -- needs either estrogen or progesterone to grow.
Aromatase inhibitors are typically used only in women past menopause. Generally, it is believed that "aromatase inhibitors don't work in younger women because [premenopausal women produce] too much estrogen," Francis said.
Francis and colleagues from the International Breast Cancer Study Group compared the different treatments in more than 3,000 women.
All had hormone receptor-positive breast cancer. About one-third were assigned tamoxifen -- another estrogen-blocker -- while one-third received tamoxifen plus ovarian suppression. The others received an aromatase inhibitor, exemestane (Aromasin), plus ovarian suppression. Each regimen lasted five years.
Most women assigned to ovarian suppression chose a monthly injection to suppress the ovaries' estrogen production. Other options were surgical removal of the ovaries or radiation of the ovaries.
Women who underwent ovarian suppression had better results than those taking tamoxifen alone. And the benefits were most pronounced in women younger than 35. However, the best results were seen when ovarian suppression was paired with the aromatase inhibitor, Francis said.
In patients who had chemotherapy and remained premenopausal, adding ovarian suppression to tamoxifen led to four or five fewer patients in 100 having a recurrence within five years, the researchers found.
But in the group that received ovarian suppression plus exemestane, seven or eight fewer patients in 100 had a recurrence within that time frame.
The researchers concluded that premenopausal women who had chemo and then took exemestane with ovarian suppression had a 35 percent decrease in risk of recurrence compared with women assigned to tamoxifen alone.
Another expert expressed some reservation about this new approach.
"It is an intriguing idea," said Dr. George Somlo, professor of medical oncology at the City of Hope Cancer Center in Duarte, Calif., who wasn't involved in the study.
But he said that a study published online in November in Annals of Oncology found a higher risk of death in younger women treated with an aromatase inhibitor.
Ovarian suppression is being used more frequently, Somlo added.
While adding different elements to treatment may boost costs, Francis said aromatase inhibitors are mostly generic now, so they are less expensive than many newer cancer drugs.
In another study to be presented at the meeting, researchers from the International Breast Cancer Intervention Study-1 reported that tamoxifen greatly reduced the risk of breast cancer in women at high risk who took it preventively.
The study enrolled more than 7,000 women, both pre- and postmenopausal, who were at high risk for breast cancer mostly because of family history. Half took 20 milligrams of tamoxifen daily for five years and the others took an inactive placebo for five years.
The women were followed for a median of 16 years (half longer, half less).
The tamoxifen reduced overall breast cancers by 29 percent, but no effect was seen for invasive estrogen receptor-negative breast cancers, according to the study. Also, among women who did develop breast cancer, no differences in breast cancer deaths were seen between the two groups, so tamoxifen's value to reduce breast cancer death risk is uncertain, the researchers said.
To learn more about aromatase inhibitors, visit BreastCancer.org.