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Am Fam Physician. 1999;59(1):176-177

Tamoxifen is currently used as adjuvant therapy for breast cancer, but it is also known to stabilize bone mineral density at various sites. Breuer and associates conducted a cross-sectional study to determine the effect of tamoxifen on the incidence of bone fracture in older residents of long-term care facilities.

Study subjects were women older than 65 years who were undergoing treatment with tamoxifen. An attempt was made to match each study subject with four women who had not been treated with this medication. The control subjects and study subjects were similar in ethnicity and age and, when possible, resided in the same nursing home. Researchers obtained minimum data set information about participants' demographics, dosage of tamoxifen and occurrence of bone fracture.

Dosage information was available for 1,373 patients who had taken tamoxifen. These women were further divided according to dosage: those taking 20 mg or more a day (91 percent) and those taking 10 mg a day (9 percent). The study subjects were then matched with 5,196 control subjects.

Of the control patients, 7.62 percent had had a fracture, compared with 6.73 percent of the women who received 20 mg of tamoxifen daily and 3.2 percent of women who received 10 mg of tamoxifen daily. When hip fracture alone was reviewed, the risk was 4.98 percent in the control group, 4.57 percent in the group that received 20 mg of tamoxifen per day and 2.4 percent in the group that received 10 mg per day. The difference between the control group and the group taking 10 mg per day nearly reached statistical significance. Adjusting for use of hormone replacement therapy did not appreciably alter the results.

The authors acknowledge some of the problems accompanying a cross-sectional study based on minimum data set information. Chronologic relationships are not always clear, and there may be inaccuracies and inconsistencies. However, they conclude that this study provides some preliminary evidence that a 10-mg daily dosage of tamoxifen is associated with a reduced risk of bone fractures in older nursing home residents.

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