In an analysis of prescribing data released early online in Cancer , researchers found that women discontinued tamoxifen at a substantially higher rate than those previously documented in clinical trials.

Researchers identified some 2800 women who were starting tamoxifen therapy through an Irish national health program that provides care to about a third of the population (based primarily on age and means testing). The cumulative rate of tamoxifen nonpersistence was about 22% after 1 year and about 35% after 3.5 years. (About a quarter of study participants discontinued tamoxifen and started another hormonal therapy within 180 days; these women were not included in the nonpersistent group.) Independent predictors of nonpersistence included age 35 to 44 years or age >75 years (compared with those aged 45 to 54 years), use of antidepressants in the preceding year, and presence of Parkinson disease or dementia.

The authors conclude that their study "demonstrates that persistence with tamoxifen cannot be assumed."

 CANCER; Published Online: January 22, 2007