TUESDAY, Feb. 7 (HealthDay News) -- A drug used to prevent
breast cancer in women at high risk for the disease appears to
cause bone loss in some postmenopausal women, a new study
The drug, Aromasin (exemestane), has been shown to reduce the
odds of breast cancer by 65 percent, but it also worsens bone
density by about three times in older women who are taking it,
Canadian researchers report.
"The drug did affect bone density at the hip and spine," said lead researcher Dr. Angela Cheung, a senior scientist at the University Health Network in Toronto. "It does not affect everyone; about 65 percent of women have some bone loss."
The fear of bone loss is not a reason not to take the drug,
Cheung said. "You really need to pay attention to your bone health
when you take this medication, especially for preventing breast
However, for women who are at high risk for fractures, other
drugs should be considered, she added.
Women taking this drug should also be taking calcium and vitamin
D supplements, and having their bone density monitored, Cheung
An older drug, tamoxifen, actually builds bone, but it is not as
effective at preventing breast cancer, she said. "But, for someone
with healthy bones it is worthwhile taking the medication."
Exemestane is an aromatase inhibitor and works by suppressing
the female hormone estrogen. These drugs are standard treatment for
postmenopausal women with early stage hormone-receptor-positive
It had been speculated that exemestane, a third-generation
aromatase inhibitor, might result in less bone loss than other
similar drugs and might even stimulate bone formation.
For the new study, Cheung's team looked at bone loss among the
more than 4,500 women who took part in a trial that compared
exemestane with a placebo.
Among women taking the drug, the risk of developing breast
cancer was lowered 65 percent, compared with women taking a
Among the 351 women in whom bone loss was studied, the
researchers found that after two years there was an 8 percent loss
of cortical bone in women taking exemestane, compared with 1
percent in the placebo group.
Cortical bone is the outer shell of bone that provides most of
the bone support, and its loss accounts for about 80 percent of
fractures in older people, the researchers noted.
The findings were published in the Feb. 6 online edition of
The Lancet Oncology.
Dr. Stephanie Bernik, chief of surgical oncology at Lenox Hill
Hospital in New York City, was somewhat cautious about the new
research. She said that "the study needs longer follow-up to see if
there is an increased risk of fracture."
"This study doesn't mean that we should stop using these drugs," she said. "We certainly rely on aromatase inhibitors more than tamoxifen in postmenopausal women, because the survival benefit has been proven."
The benefit of the drug outweighs that risk for most women, she
said. However, if there is a family history of osteoporosis it may
not be the best choice, Bernik said.
For more on breast cancer, visit the
American Cancer Society.