Tamoxifen discontinuation surprisingly high

DUBLIN, Ireland, Jan. 22 (UPI) -- An Irish study found 25 percent of women treated for breast cancer stop the drug tamoxifen within one year -- twice as high as expected.

Early termination of the breast-cancer drug may negatively affect treatment efficacy, according to study leader Thomas I. Barron of Trinity College in Dublin and St. James's Hospital.

Barron reviewed pharmaceutical data from a national database of 2,816 women age 35 and older who started tamoxifen for breast cancer.

The researchers found that at 12 months 22 percent of women had ceased using the drug. At 24 months 28 percent had stopped tamoxifen, and at 3.5 years 35 percent had stopped the treatment without commencing an alternative therapy, according to the study published in the March issue of the journal Cancer.

Tamoxifen is a selective estrogen receptor modulator that inhibits the stimulatory effect that estrogen has on the development of specific types of breast cancer.