TAMOXIFEN INCREASES SPINAL BONE MINERAL DENSITY IN POSTMENOPAUSAL WOMEN

TAMOXIFEN INCREASES SPINAL BONE MINERAL DENSITY IN POSTMENOPAUSAL WOMEN, according to results of a two-year, prospective, randomized, double-blind trial conducted by Richard Love, MD, et al., University of Wisconsin, published in the March 26 New England Journal of Medicine. The study included 140 postmenopausal women with axillary node-negative breast cancer who received either 10 mg of tamoxifen (ICI's Nolvadex) orally twice daily or placebo. Bone density was measured by dual-photon absorptiometry at 0, 3, 6, 12, 18 and 24 months of treatment.

Results showed that women given tamoxifen exhibited a .61% increase per year in mean bone mineral density of the lumbar spine, compared to women enrolled in the placebo group, who had an annual decrease of 1%. However, "radial bone mineral density decreased to the same extent in both groups," the authors noted. In other measurements, the trial found a reduction in serum concentrations of osteocalcin and alkaline phosphatase in the tamoxifen group, which "presumably reflects decreased bone turnover or bone remodeling."

Overall, "the 3% difference in lumbar-spine bone mineral density between the tamoxifen and placebo groups at the end of two years is identical to the difference induced in women given etidronate [Norwich Eaton's Didronel PMO] for osteoporosis but is lower than the difference of 5%-10% induced during the same period in women given calcitonin or estrogen for that disorder," the researchers stated. An FDA advisory committee declined to recommend Didronel PMO for approval in March 1991 after a followup study showed a 50% increase in new vertebral fractures during the third year of treatment ("The Pink Sheet" March 11, 1991, p. 3).

The study adds that "estrogen also has a stabilizing effect on radial bone, an effect not found in our short-term study. If further data can be collected on the effects of tamoxifen on the radius and femur, this agent could be considered an alternative treatment for stabilizing bone mass, particularly in women in whom estrogens or bisphosphonates are contraindicated."

The study was conducted to answer yet another question about long-term use of tamoxifen prior to the startup of the largest breast cancer prevention trial to date. The same researchers reported in December that tamoxifen resulted in favorable effects on lipid concentrations.

The National Institutes of Health is expected to announce the start of the trial at the end of April. The prospective multicenter trial, which has a randomized, placebo-controlled, double-blind design, is expected to enroll approximately 16,000 women over the age of 35 who are at increased risk of developing breast cancer.