Study: Anastrozole Leads to Few More Bone Fractures Than Tamoxifen

Breast cancer patients taking anastrozole instead of tamoxifen have slightly more bone fractures but the difference is not statistically significant, according to results from the largest study ever undertaken with cancer patients.

The news, reported at the European Cancer Conference by Dr. Anthony Howell of Christie Hospital, Manchester, UK, seems likely to erase concern that a higher incidence of bone fractures might outweigh the benefits of anastrozole.

While studies have shown astrozole to be more effective than tamoxifen as an estrogen-receptor blocker, it also leads to "profound estrogen deprivation." Since estrogen is needed to maintain bone health, some researchers have questioned whether the risks of weaker bones caused by taking anastrozole were serious enough to reconsider use of the drug.

In a study involving 400 centers in 21 countries in which 3,125 patients received anastrozole and 3,116 received tamoxifen, the overall fracture rate among anastrozole users was 7.1 percent compared to 4.4 percent for tamoxifen users.

There were more hip fractures in the tamoxifen group, but this difference was only 0.1 percent. There were slightly more fractures of the spine and more Colles fractures in the anastrozole group, but the differences were not statistically significant.

Given anastrozole's more positive profile with respect to endometrial cancers and thromboembolic events compared to tamoxifen, Howell said it would appear that the slight increase in the risk of bone fractures is outweighed by the lower risk of either of those other two side-effects.

Other Sources: European Cancer Conference