EFFECT OF LONG-TERM TAMOXIFEN THERAPY ON CANCELLOUS BONE REMODELING AND STRUCTURE IN WOMEN WITH BREAST-CANCER

The effects of long-term tamoxifen therapy on bone remodeling were stu died in 41 women with breast cancer, 22 treated with tamoxifen for a m inimum of 15 months (mean 33) and 19 untreated. Transiliac crest 1 bon e biopsies were obtained and a comprehensive histomorphometric analysi s performed using a semiautomatic image analysis system. There were no statistically significant differences between the two groups in bone area, osteoid perimeter and area, or osteoid width. Mineral apposition al rate, adjusted appositional rate, and mineralization lag time were also similar in the two groups; however, tissue-based bone formation r ate was significantly lower in the tamoxifen-treated women (p = 0.05) and the remodeling period significantly longer (p < 0.05). Mean and ma ximum resorption cavity depth and cavity area were significantly reduc ed in the tamoxifen-treated patients compared to the untreated patient s (p < 0.01, P < 0.01, and p < 0.03, respectively). Calculated and dir ectly measured indices of cancellous bone structure were similar in th e two groups, although the data indicated a trend toward greater conne ctedness in the tamoxifen-treated group. These data indicate that tamo xifen does not exert an antiestrogenic effect on bone remodeling in th e human and are consistent with a weak estrogenic effect.