MONDAY, June 6, 2016 (HealthDay News) — Many survivors of breast cancers that are sensitive to estrogen are advised to take hormone-suppressing drugs such as tamoxifen for five years, to cut their odds for a recurrence. Tamoxifen can have onerous side effects, however. Now, new research finds that taking an alternative, and less troublesome, class of medications for a full decade can reduce the risk for recurrence even more—without affecting a woman's quality of life.
The newer class of hormone-suppressing drugs are called aromatase inhibitors, and include drugs such as letrozole (Femara), anastrozole (Arimidex) and exemestane (Aromasin).
"Aromatase inhibitors do not have all the side effects of tamoxifen and overall are much better tolerated than tamoxifen," explained one breast cancer expert, Dr. Stephanie Bernik.
She believes the new study supports the benefit of aromatase inhibitors, and "women are much more likely to continue a longer course with this therapy" than with tamoxifen.
The study findings were presented Sunday in Chicago at the annual meeting of the American Society for Clinical Oncology (ASCO).
The new research involved more than 1,900 postmenopausal women who had already received five years of Femara treatment after surviving an early stage, hormone-sensitive form of breast cancer.
Some of the women continued receiving Femara for another five years, while others received a placebo.
Those who received Femara for the five additional years had a 34 percent lower risk of breast cancer recurrence than those who received the placebo, said a team led by Dr. Paul Goss, professor of medicine at Harvard Medical School.
There were also no significant differences in the women's overall quality of life, or menopausal symptoms, between the two groups.
While the rate of breast cancer recurrence was lower with the extended therapy, the approach did not seem to have any effect on the women's overall odds of dying from any cause, the researchers noted.
According to Goss, "women with early stage hormone-receptor positive breast cancer face an indefinite risk of relapse.
"The study provides direction for many patients and their doctors, confirming that prolonging aromatase inhibitor therapy can further reduce the risk of breast cancer recurrences," said Goss, who also directs Breast Cancer Research at Massachusetts General Hospital.
In an ASCO news release, he said that "longer [aromatase inhibitor] therapy also showed a substantial breast cancer preventative effect in the opposite, healthy breast."
For her part, Bernik noted that "many women don't want to take tamoxifen because of the side effects."
Those side effects can include "hot flashes, increased rate of uterine cancer, DVTs [clots in the deep veins of the leg that can break off and travel to the lung], increased rate of strokes, amongst other risks," said Bernik, who is chief of surgical oncology at Lenox Hill Hospital, in New York City.
She said that many experts had assumed that a 10-year course of aromatase inhibitors like Femara might be a safe, attractive alternative to tamoxifen for patients—but no study had yet supported that notion.
"Therefore it is exciting that a new study backs the assumption of the added benefit of an extended course of the drug," Bernik said.
According to background information supplied by the researchers, in 2012, there were more than 6 million women worldwide who had survived at least five years after a breast cancer diagnosis. Most of them had estrogen receptor-positive breast cancer, Goss' team said.
Because the new findings were presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.
The U.S. National Cancer Institute has more on breast cancer.