New Effects of Tamoxifen Found

A new study on tamoxifin has found that while use of the drug decreases the risk of a second breast cancer, it also may cause a fivefold increased risk of estrogen-receptor (ER)-negative breast cancer in the healthy breast. Conducted by researchers from the Fred Hutchinson Cancer Research Center (Seattle, WA, USA), the study was published in the July 4, 2001, issue of the Journal of the National Cancer Institute.

The study involved nearly 9,000 women diagnosed between 1990 and 1998 with primary localized or regional-stage cancer in one breast. The women, 50 years or older, were followed until cancer developed in the other breast or they died or the study ended (December 1999). Overall, 89 women developed cancer in the opposite breast. Among nonusers, 100 developed a tumor on the other side. The data showed that 27% of the contralateral tumors that developed were ER-negative, while only 4% of the tumors in nonusers were ER-negative. In addition to being more difficult to treat, ER-negative tumors are associated with a higher mortality rate and an 8-35% lower five-year survival rate.

"While this study, if confirmed by others, adds to our knowledge about the effects of tamoxifin, I do not believe it should change current clinical practices, as tamoxifin has clearly been shown to reduce the risk of recurrence and improve survival among women diagnosed with breast cancer,” said Christopher Li, M.D., a member of the research team.




Related Links:
Fred Hutchinson Cancer Center
National Cancer Institute