Chemotherapy leads to bone loss.

Between 50 and 70 percent of women undergoing chemotherapy for breast cancer stop having regular menstrual cycles. A new study shows that these women also begin to lose bone mass within 6 months of starting chemotherapy.

"Bone loss occurs early and rapidly, and this is an under-appreciated side effect" of chemotherapy, says Charles L. Shapiro of Ohio State University in Columbus.

He and his colleagues studied 49 women who received 3 or 6 months of chemotherapy for early-stage breast cancer. Of these women, 35 missed their menstrual cycles for 1 year and so were diagnosed with ovarian failure. Within 6 months of starting their treatments, they also lost about 4 percent of the bone density in their spines. After another 6 months, the women had lost an additional 3.7 percent of spinal bone mass.

Tests on the women's thighbones showed a 2.6 percent loss at 6 months after starting chemotherapy and another 2 percent loss by the time a year had passed.

In contrast, the 14 women who retained ovarian function and continued their menstrual cycles didn't lose bone mass over the course of the year, Shapiro and his colleagues report in the July 15 JOURNAL OF CLINICAL ONCOLOGY. A woman who has reached menopause--the time when her ovaries fail naturally--can lose up to 2 percent of her bone density each year, Shapiro says. Ovaries produce the sex hormone estrogen, which plays an essential role in maintaining bone mass.

The researchers are beginning a study of 400 women receiving chemotherapy for breast cancer to determine whether they benefit from simultaneously taking drugs that prevent bone loss.