['Apolipoprotein E4 (APOE4) allele is an important risk factor for breast cancer and affects clearance of chylomicron remnants. Tamoxifen therapy increases serum triglyceride levels and sometimes inducing severe hypertriglyceridemia in breast cancer patients.', 'Thirty-three women with breast cancer were recruited to examine the APOE polymorphism and fasting plasma lipid profiles before and after tamoxifen treatment for 6 months.', 'We found that plasma lipid profiles changed in accordance with the APOE4 allele after tamoxifen treatment for 6 months. Especially plasma triglyceride levels significantly decreased in the APOE4-positive patients (p=0.025), while there was no change in APOE4-negative patients (p=0.189). The total plasma cholesterol levels were reduced in APOE-4 positive patients after 6-month tamoxifen treatment (p=0.014). The levels of plasma low density lipoprotein cholesterol and high density lipoprotein cholesterol significantly decreased in both APOE4-negative and APOE4-positive patients.'] Does apolipoprotein E4 allele influence the response of plasma triglyceride levels to tamoxifen in breast cancer patients?