SOURCES: Charles L. Shapiro, M.D., co-director, Dubin Breast Center, and director, Translational Breast Cancer Research, Tisch Cancer Institute at Mount Sinai, New York City; Ruby Sharma, M.D., oncologist, North Shore-LIJ Cancer Institute, Lake Success, N.Y.; The Lancet, news release, July 23, 2015
THURSDAY, July 23, 2015 (HealthDay News) -- There's more evidence that two classes of inexpensive generic drugs reduce the risk of death in postmenopausal women with early breast cancer, a pair of new British studies find.
The two classes of drugs -- called aromatase inhibitors and bisphosphonates -- can also be used together to increase the benefits and reduce some side effects, according to the authors of the studies published July 23 in The Lancet.
Aromatase inhibitors include drugs such as anastrozole, letrozole and exemestane, while bisphosphonates include drugs such as zoledronic acid.
The two new studies "provide really good evidence that both of these inexpensive generic drugs can help to reduce breast cancer mortality in postmenopausal women," Richard Gray, the University of Oxford lead statistician for both studies, said in a journal news release.
The studies were released by The Early Breast Cancer Trialists' Collaborative Group, a worldwide collaboration set up 30 years ago by researchers at Oxford.
The first study looked at data from 30,000 postmenopausal breast cancer survivors who took part in nine clinical trials. After five years of treatment, those who took an aromatase inhibitor had a slightly better survival rate than those who took standard hormonal therapy (tamoxifen).
After another five years of treatment, taking an aromatase inhibitor further reduced the risk of cancer recurrence by 30 percent and the risk of dying from breast cancer by about 15 percent, compared to taking tamoxifen, the study found.
Compared to no endocrine treatment, taking aromatase inhibitors would reduce the risk of dying from breast cancer by about 40 percent over the decade after starting treatment, the researchers estimated.
The second study included data from about 19,000 other breast cancer survivors who took part in 26 clinical trials. This study found that two to five years of treatment with bisphosphonates -- drugs usually used to treat osteoporosis -- reduced the risk of cancer recurrence and significantly extended survival in postmenopausal women.
The risk of death from breast cancer after 10 years was 14.7 percent in women who took bisphosphonates and 18 percent in women who did not take the drugs, the study found.
However, bisphosphonates appeared to have little effect in premenopausal patients.
"About two-thirds of all women with breast cancer are postmenopausal with hormone-sensitive tumors, so could potentially benefit from both drugs," Gray said.
He added that the drugs often complement each other, because the main side effect of aromatase inhibitors is an increase in bone loss and fractures, while bisphosphonates reduce that risk and improve survival.
Two experts in the United States said the findings are important, although caveats remain for both classes of drugs.
The first study "shows a clear-cut, though small, absolute survival advantage of aromatase inhibitors over tamoxifen in postmenopausal women," said Dr. Charles Shapiro, co-director of the Dubin Breast Cancer Center at the Tisch Cancer Institute at Mount Sinai in New York City.
But he added that the drugs are not without risks. "The side effects of aromatase inhibitors, which include joint pains, vaginal dryness and others, are such that about 20 percent of women cannot complete the recommended five-year duration of these drugs," Shapiro said.
And while the bisphosphonates did show "very small absolute benefits" for patients, "the optimal drug and schedule of administration of these drugs has yet to be defined," he added.
Dr. Ruby Sharma is an oncologist at North Shore-LIJ Cancer Institute in Lake Success, N.Y. Regarding aromatase inhibitors, she said that in her practice, patients entering or in menopause "are treated with two years of tamoxifen, and then I switch to aromatase inhibitors once menopause is confirmed."
Regarding bisphosphonates, Sharma said that although the study results were positive, giving the drugs to postmenopausal women with early breast cancer is not yet "an accepted standard of care yet due to negative data from several other studies."
However, "there seems to be benefit in a subset of women," she said, and "I definitely use bisphosphonates for my postmenopausal breast cancer patients with osteoporosis."
The American Academy of Family Physicians has more about breast cancer.