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Tamoxifen Treatment for Breast Cancer and Risk of Endometrial Cancer: A Case-Control Study

Anthony J. Swerdlow, Michael Emlyn Jones, For the British Tamoxifen Second Cancer Study Group

JNCI Journal of the National Cancer Institute, 2005

1,067 participants · 230 citations

Abstract

BACKGROUND: Tamoxifen treatment of breast cancer is associated with an increased risk of endometrial cancer, but tamoxifen-related risks of endometrial cancer are unclear in premenopausal women, in long-term users of tamoxifen, and in women for whom several years have passed since ending treatment. We conducted a case-control study in Britain to investigate these risks. METHODS: We compared treatment information on 813 case patients who had endometrial cancer after their diagnosis for breast cancer and 1067 control patients who had breast cancer but not subsequent endometrial cancer. We assessed risk by conditional logistic regression analysis. All statistical tests were two-sided. RESULTS: Overall, tamoxifen treatment, compared with no treatment, was associated with an increased risk of endometrial cancer (odds ratio [OR] = 2.4; 95% confidence interval [CI] = 1.8 to 3.0). Risk increased statistically significantly (P(trend) or =5 years of treatment compared with no treatment, OR = 3.6, 95% CI = 2.6 to 4.8). As an indication of background levels of treatment, 16% of control patients received 5 years or more of treatment. Risk of endometrial cancer adjusted for treatment duration did not diminish in follow-up to at least 5 years after the last treatment ended. Risk of endometrial cancer was not associated with the daily dose of tamoxifen and was comparable in pre- and postmenopausal women. Ever treatment with tamoxifen was associated with a much greater risk of Mullerian and…

How strong is the evidence?

Evidence Hub reads this as a case-control, done in people. Its evidence level is 4 of 5 (Low · observational). Observational designs can show an association but not prove cause. Reported size: 1,067 participants or records.

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