Tamoxifen discontinuation rates surprisingly high in clinical practice

Breast Cancer Treatment and Tamoxifen

In the clinical practice setting almost a quarter of women treated for breast cancer stop tamoxifen within one year, a rate twice as high as indicated by previous studies. The new study, published in the March 1, 2007 issue of CANCER, a peer-reviewed journal of the American Cancer Society, says early termination of this highly effective breast cancer drug may negatively affect treatment efficacy. At 3.5 years, the study also reveals that over one third of women have ceased tamoxifen treatment.

Tamoxifen is a selective estrogen receptor modulator that inhibits the stimulatory effect that estrogen has on the development of specific types of breast cancer. Scientists estimate that over 40,000 recurrences are prevented each year worldwide because of this drug. However, the optimal duration of therapy is five years. Less than five years of continual treatment is associated with higher rates of recurrence and higher mortality rates. The most common reason for discontinuation is adverse effects, including mood swings and hot flashes; these are often successfully treated with a specific antidepressant.

Discontinuation or non-persistence rates estimated by clinical trials range from 16 to 32 percent. Studies of usage outside clinical trials report non-persistence rates of only 17 percent at two years and 31 percent at five years. However, these rates are compiled from self-reporting data collection methods and target elderly patients