NEW YORK (Reuters Health) – While raloxifene and tamoxifen are broadly similar in reducing breast cancer risk, raloxifene appears also to lower the odds of developing endometrial cancer, researchers report in the September 1st issue of the Journal of Clinical Oncology.

“These data are important,” lead investigator Dr. Angela DeMichele told Reuters Health, “because they suggest a critical difference between tamoxifen and raloxifene that could help physicians in tailoring therapy to the patient.”

She added, “A randomized clinical trial has shown that the drugs are roughly equivalent in term of their ability to prevent breast cancer.”

To examine the effect of raloxifene and tamoxifen on endometrial cancer risk, Dr. DeMichele of the University of Pennsylvania, Philadelphia and colleagues examined data on 547 women who were diagnosed with endometrial cancer and 1410 controls.

Some 3.3% of the cases had taken raloxifene compared to 6.6% of the controls. Corresponding proportions for tamoxifen were 6.2% and 2.4%.

After adjustment for other risk factors, the risk of endometrial cancer in raloxifene users was half that of nonusers (odds ratio = 0.50). Tamoxifen users were three times more likely to develop endometrial cancer than were raloxifene users (odds ratio = 3.0).

Overall, raloxifene users were at significantly reduced risk of endometrial cancer compared to both tamoxifen users and women who did not use a selective estrogen receptor modulator.

Given the similarity in protection against breast cancer, continued Dr. DeMichele “a secondary benefit, like a reduction in the risk of endometrial cancer, may be very important to patients who have not had a hysterectomy and are concerned about the increased risk of endometrial cancer with tamoxifen.”

Reference:
J Clin Oncol 2008;26:4151-4159.