Effects of Toremifene and Tamoxifen on Lipid Profiles in Post-menopausal Patients with Early Breast Cancer: Interim Results from a Japanese Phase III Trial

Toremifene and tamoxifen have been used for adjuvant therapy in post-menopausal patients with breast cancer in Japan. Dyslipidemias are common in post-menopausal women. However, limited data are available on the effects of these agents on lipid profiles in Japanese patients. The Japan Toremifene Cooperative Study Group has been conducting a Phase III randomized trial of post-menopausal patients with breast cancer. One of its secondary endpoints is to confirm the effects of these agents on serum lipid profiles. The subjects were post-menopausal Japanese patients who had undergone surgery for early breast cancer. Toremifene or tamoxifen was administered for 2 years. Lipid levels were measured before and up to 24 months after initiation. Compared with baseline, at 24 months, the toremifene group (n = 123) showed significantly decreased total cholesterol (P < 0.001) and low-density lipoprotein cholesterol levels (P < 0.001), and significantly increased high-density lipoprotein cholesterol levels (P < 0.001). Their triglyceride levels were not affected (P = 0.677). The tamoxifen group (n = 120) also showed significantly decreased total cholesterol (P < 0.001) and low-density lipoprotein cholesterol levels (P < 0.001); no significant changes occurred in high-density lipoprotein cholesterol (P = 0.297) or triglyceride levels (P = 0.120). Distinct differences between two selective estrogen receptor modulators on lipids were observed. Toremifene improved lipid profiles, particularly as an enhancer of high-density lipoprotein cholesterol. To a large extent, tamoxifen improved low-density lipoprotein cholesterol levels. The impact of these improved lipid profiles on the risk of cardiovascular diseases needs further confirmation.