Tamoxifen for the prevention of breast cancer: late results of the Italian Randomized Tamoxifen Prevention Trial among women with hysterectomy.

BACKGROUND: Initial findings of the Italian Randomized Tamoxifen Prevention Trial found no reduction in risk of breast cancer with tamoxifen use, whereas the National Surgical Adjuvant Breast and Bowel Project Breast Cancer Prevention Trial showed that tamoxifen treatment reduces risk of estrogen receptor-positive breast cancer. Here we present an extended follow-up of the Italian trial. METHODS: From October 1, 1992, to December 31, 1997, 5408 otherwise healthy women who had undergone hysterectomy were randomly assigned in a double-blind manner to tamoxifen (20 mg daily) or placebo for 5 years. Rates of breast cancer and other events in the two groups were compared by the use of risk ratios (RRs) and 95% confidence intervals (CIs). RESULTS: After 11 years of follow-up, 136 women (74 placebo, 62 tamoxifen) developed breast cancer (RR = 0.84, 95% CI = 0.60 to 1.17; annual rates were 2.48 and 2.07 per 1000 women-years, respectively). The rates of breast cancer in the two study groups were similar among women who had had bilateral oophorectomy and among women at low risk for hormone receptor-positive (HR+) disease but were much lower in the tamoxifen group among women at high risk (placebo, 6.26 per 1000 women-years, tamoxifen, 1.50 per 1000 women-years; RR = 0.24, 95% CI = 0.10 to 0.59). During the treatment period, women in the tamoxifen group reported more hot flashes (RR = 1.78, 95% CI = 1.57 to 2.00), vaginal discharge (RR = 3.44, 95% CI = 2.90 to 4.09), and urinary disturbances (RR = 1.52, 95% CI = 1.23 to 1.89) but fewer headaches (RR = 0.68, 95% CI = 0.50 to 0.94) than women in the placebo group. Hypertriglyceridemia (RR = 4.33, 95% CI = 1.96 to 9.53), thromboembolic events (RR = 1.63, 95% CI = 1.02 to 2.62), and cardiac arrhythmia or atrial fibrillation (RR = 1.73, 95% CI = 1.01 to 2.98) were also more frequent in the tamoxifen group than in the placebo group. CONCLUSIONS: Appropriate selection of women at high risk for HR+ disease may improve the risk-benefit ratio of tamoxifen intervention.

Effect of tamoxifen on venous thromboembolic events in a breast cancer prevention trial.

BACKGROUND: Tamoxifen, a selective estrogen-receptor modulator, increases venous thromboembolic events (VTE), but the factors explaining this risk are unclear. Atherosclerosis may induce VTE, or the 2 conditions may share common risk factors. We assessed the effect of tamoxifen on VTE in a breast cancer prevention trial and studied its association with risk factors for VTE. METHODS AND RESULTS: The incidence of VTE was studied in 5408 hysterectomized women randomly assigned to tamoxifen 20 mg/d or placebo for 5 years. There were 28 VTEs on placebo and 44 on tamoxifen therapy (hazard ratio [HR]=1.63; 95% confidence interval [CI], 1.02 to 2.63), 80% of which were superficial phlebitis, accounting for all of the excess due to tamoxifen within 18 months from randomization. Compared with placebo, the risk of VTE on tamoxifen was higher in women aged 55 years or older, women with a body mass index > or =25 kg/m2, elevated blood pressure, total cholesterol > or =250 mg/dL, current smoking, and a family history of coronary heart disease (CHD). Of the 685 women with a CHD risk score > or =5 who entered the trial, 1 in the placebo arm and 13 in the tamoxifen arm developed VTE (log-rank P=0.0013). In multivariate regression analysis, age > or =60 years, height > or =165 cm, and diastolic blood pressure > or =90 mm Hg had independent detrimental effects on VTE risk during tamoxifen therapy, whereas transdermal estrogen therapy concomitant with tamoxifen was not associated with any excess of VTE (HR=0.64; 95% CI, 0.23 to 1.82). CONCLUSIONS: Women with conventional risk factors for atherosclerosis have a higher risk of VTE during tamoxifen therapy. This information should be incorporated into counseling women on its risk-benefit ratio, particularly in the prevention setting.