Dec. 14, 2007 (San Antonio) -- The bone-building drugs known as bisphosphonates can offset a side effect of hormone therapy for breast cancer -- significant bone loss that can lead to fractures, three new studies suggest.
Researchers from the Austrian Breast and Colorectal Cancer Study Group report that the drug Zometa helped to build bone in premenopausal women taking Arimidex for breast cancer. Arimidex is a hormone therapy used in breast cancer patients that helps lower estrogen levels.
U.S. researchers found that postmenopausal women taking another hormone therapy used in breast cancer patients -- Femara -- were less likely to suffer bone loss if they received concomitant treatment with Zometa.
And British researchers say the biphosphonate Actonel helped to preserve bone in women taking Arimidex.
Hormone Therapy Causes Bone Loss
About 70% of women with breast cancer have tumors that are fueled by estrogen, making hormone therapy a cornerstone of regimens to prevent recurrences and improve survival.
More recently, they started using the more potent hormone treatments called aromatase inhibitors to shrink tumors. The drugs block an enzyme the body uses to make estrogen, thereby slashing the body's production of estrogen altogether.
These drugs can be lifesaving, but suppressed estrogen levels increase bone turnover and accelerate bone loss, says Adam Brufsky, MD, of the University of Pittsburgh. He led the American study.
Bisphosphonates increase bone formation and decreasing bone turnover, he explains.
"Aromatase inhibitors cause bone loss and these drugs can ameliorate that loss," says Eric Winer, MD, a breast cancer specialist at the Dana-Farber Cancer Institute in Boston who wasn't involved with the work.
The research was presented here at the annual San Antonio Breast Cancer Symposium.
Zometa Helps Build Bone
The Australian study involved over 400 premenopausal women with early-stage breast cancer; they received hormone therapy to prevent recurrence of breast cancer. The women were being treated by tamoxifen and Zoladex, or Arimidex and Zoladex.
In addition, half the women received treatment with the bone-building drug Zometa. The medication was given once every six months for three years.
Bone density measurements of the spine were taken at the beginning of the study and two years after treatment ended.
Results show that women who did not receive Zometa during hormonal therapy lost 6.3% of their bone mineral density.
In contrast, bone mineral density increased by 4.4% in women who took Zometa, says researcher Michael Gnant, MD, of the University of Vienna in Austria.
Zometa Helps Prevent Bone Loss
The American study, funded by Zometa maker Novartis Pharmaceuticals, involved over 600 postmenopausal women starting Femara treatment.
Half were given Zometa as soon as they started taking Femara for prevention of breast cancer recurrence. The rest were given Zometa only if researchers detected significant bone loss or a fracture.
Over the next three years, bone mineral density in the spine increased by an average of 4% in women who got Zometa from the start. Their hip bone mineral density rose by an average of 2%.
In contrast, the group in which treatment was delayed showed an average decrease of 3% in the spine bone density and an average decrease of 4% in hip density.
The ongoing British study involves 250 women enrolled in testing whether the aromatase inhibitor Arimidex can help to prevent breast cancer in high-risk women.
Half the women are taking one Arimidex tablet a day for five years, while the others are taking placebo.
Early results show that women with normal bone mineral density at the start of the study who weren't given the osteoporosis drug Actonel lost a significant amount of bone on Arimidex treatment.
However, bone mineral density increased in women on Arimidex with poor bone health at the start of the study who were given Actonel for one year, says researcher Shalini Singh, MD, of the Wolfson Institute of Preventive Medicine in London.