The results were so startling the doctors halted their original study so the women -- some of whom lost as much as 8% of their bone in just one year -- could receive treatment to prevent further loss that can lead to fractures as they age.
"Eight percent bone loss in the spine is roughly four [times] the normal postmenopausal bone loss," says Charles L. Shapiro, MD, author of the report that appears in the July 15 issue of the Journal of Clinical Oncology.
He and colleagues from the Dana-Farber Cancer Institute and Brigham and Women's Hospital in Boston made the discovery while conducting a study of the effects of chemotherapy on the bones of women undergoing chemotherapy for early-stage breast cancer. Although they expected to find some adverse effect on women's bones, Shapiro says it was far more rapid and dramatic than they expected.
Of the 49 women in the study, 35 entered early menopause due to chemotherapy, which is not uncommon. But what was uncommon was that compared with the women who did not experience early menopause, those who did had dramatic bone loss at their spine and thigh bones within a few months of starting chemotherapy.
Shapiro and colleagues believe the sudden drop in estrogen that accompanies chemotherapy-induced early menopause is responsible for the bone loss. Estrogen is known to be important to keeping bones healthy. Protecting against bone loss and osteoporosis is a main reason women are encouraged to take estrogen replacement therapy after menopause.
"For those women with breast cancer who undergo early menopause from chemotherapy I think they should have bone mineral density checked, they should be encouraged to take adequate calcium and vitamin D, they should be encouraged to start adopting a moderate-weight bearing exercise program, and they should be counseled about [behaviors such as] smoking and alcohol that tend to worsen bone loss," Shapiro tells WebMD.
Overall, the results of the study are "remarkable," says Theodora Ross, MD, PhD.
"It could really change how we give chemotherapy," says Ross, a breast cancer specialist at the University of Michigan Comprehensive Cancer Center in Ann Arbor. She says the idea of adding bisphosphonate drugs like Zometa to chemotherapy probably will now be taken much more seriously by cancer researchers because the implications are so great for the millions of younger women with breast cancer.
Richard Theriault, DO, of the M.D. Anderson Cancer Center in Houston, agrees.
"I suspect that as soon as this paper is published people will start adapting it," says Theriault, of the division of breast medical oncology. "We're going to cure a lot of these women and they're going to live a long time and they're all going to have osteoporosis unless we do something."