Serum lipid levels during and after adjuvant toremifene or tamoxifen therapy for breast cancer

Tamoxifen decreases serum cholesterol (S-cholesterol) level about 10% and low-density lipoprotein cholesterol (S-LDL) 15–20%, but in most studies it has increased serum triglyceride levels and had little effect on serum high-density cholesterol (S-HDL). The effect of another antiestrogen, toremifene, on the serum lipid profile has not been completely studied. We monitored serum lipid levels longitudinally in 141 axillary node-positive postmenopausal breast cancer patients who received randomly either 40 mg toremifene or 20 mg tamoxifen as adjuvant therapy for 36 months, and in 34 postmenopausal women who received no adjuvant systemic therapy after surgery for axillary node-negative breast cancer. No significant differences were found between the drugs in their effects on S-cholesterol, LDL, HDL, or triglyceride levels, or on the cholesterol-to-HDL or LDL-to-HDL ratios. For both drugs the S-cholesterol and S-LDL absolute lowering effect was the greater the higher the pretreatment level. For a patient with a median pretreatment value, toremifene decreased S-cholesterol 6% and tamoxifen 13%, and S-LDL decreased by 13% and 23%, respectively, at 6 months of therapy. Six months after stopping three-year antiestrogen therapy S- cholesterol and S-LDL levels had returned to the pretreatment levels. In conclusion, we found no major differences between 40 mg toremifene and 20 mg of tamoxifen in their effect on the serum lipid levels, which return to the pretreatment levels within 6 months after cessation of therapy.