Background: Adjuvant tamoxifen therapy for breast cancer has been given for a period of several years. Cardiovascular diseases increase in incidence rapidly in women older than 60 years. Favorable changes in cardiovascular risk factors have been seen with 2 years of tamoxifen therapy, and lower rates of myocardial infarction and of hospitalization for heart disease have been observed in tamoxifen-treated women. Purpose: We sought to evaluate changes in risk factors for cardiovascular diseases in postmenopausal women after therapy with tamoxifen for 5 years. Methods: Five years after their initial entry in a 2-year randomized, placebo-controlled toxicity study, we re-examined 62 of the original 140 disease-free, axillary node-negative postmenopausal breast cancer patients. These 62 patients were women available for study because they had not suffered major illness and had continued on either the tamoxifen or notamoxifen regimen to which they had been originally randomly assigned for the entire 5 years. Patient and control blood samples were analyzed for total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol and subfractions, triglycerides, apolipoprotein AI, apolipoprotein B, lipoprotein(a), fibrinogen, glucose, and platelets. Results: At base line for all measurements except atherogenic lipoprotein [lipoprotein(a)], the 30 long-term tamoxifen recipients and the 32 long-term no-tamoxifen recipients were not significantly different. After 5 years, levels of total serum cholesterol (P<.001), LDL cholesterol (P<.0001), and lipoprotein(a) (P = .001) were significantly lower, and apolipoprotein AI levels were significantly higher (P<.001) in the tamoxifen-treated group compared with the no-tamoxifen group. Apolipoprotein B levels increased to a greater extent in the no-tamoxifen than in the tamoxifen group (P<.001). After 5 years, fibrinogen level decreases and triglyceride level increases in the tamoxifen group compared with the notamoxifen group were of borderline statistical significance and HDL cholesterol levels were not different in the two groups. Conclusion: Favorable changes in lipid, lipoprotein, and fibrinogen levels seen early in tamoxifen therapy in postmenopausal women persist with treatment of 5 years. Implications: The types and magnitude of changes in cardiovascular risk factors seen here with tamoxifen are similar to a certain extent with those seen with estrogen supplements. Further risk-factor and ethnic-group data are needed to estimate the magnitude of expected benefits of tamoxifen treatment on incidence of heart disease.
