Tamoxifen, a common drug used to treat breast cancer, works by blocking the effect of estrogen on tumor cells. The drug is especially effective in women who have hormone-responsive tumors. A recent study published in the Journal of Clinical Oncology
reported that women who completed their 5-year course of tamoxifen had a 40% chance of reoccurrence as opposed to 46% chance in women who stopped taking tamoxifen after only 2 years.
The study recruited 3449 women between 1987 and 1997. The study cohort was comprised of international women over 50 who had cancer in one breast. Of the 3449 total sample, 1724 women were assigned to tamoxifen therapy for 2 years and 1725 women were assigned to tamoxifen therapy for 5 years.
The study found that 2 years of tamoxifen therapy was associated with a 29% reduction in cancer recurrence and a 17% reduction in deaths over 10 years. Women who received 5 years of tamoxifen therapy showed better results with a 46% reduction in cancer recurrence and a 26% reduction in deaths over a period of 10 years.
The research study concluded that in addition to reducing the risk for recurrence, taking tamoxifen for a 5-year period also prevented the occurrence of new tumors in the second breast. This study is significant because many women stop taking tamoxifen before the 5-year period, most times due to negative side effects experienced while taking the drug. The results of this long-term study indicate that women should be encouraged to take the full course of treatment of tamoxifen therapy.
Hackshaw A, Roughton M, Forsyth S et al. Long-term benefits of 5 years of tamoxifen: 10-year follow-up of a large randomized trial in women at least 50 years of age with early breast cancer.J Clin Oncol. 2011 March 21 [Epub ahead of print].