Effect of tamoxifen on lipoprotein(a) and insulin-like growth factor-I (IGF-I) in healthy women

Studies in breast cancer patients have shown that tamoxifen decreases circu lating levels of Lipoprotein(a) (Lp(a)), an independent risk factor for pre mature coronary heart disease, and insulin-like growth factor-I (IGF-I), a promising surrogate biomarker for breast cancer. Since a common hormone reg ulatory pathway has been suggested for both biomarkers, we measured LP(a) l evels for 6 months in 68 healthy women participating in a chemoprevention t rial of tamoxifen and correlated its changes with IGF-I. After 1 month, mea n Lp(a) levels decreased by 23% with tamoxifen and increased by 6% with pla cebo (P = 0.033). No further change was observed after 2 and 6 months. Wome n with abnormal values at baseline (i.e. > 30 mg/dl) showed the highest red uction. The mean levels of IGF-I decreased by 23.5% with tamoxifen and rema ined stable with placebo, but the changes induced by tamoxifen in Lp(a) and IGF-I levels were uncorrelated. Our results support the observation that t amoxifen may be a suitable preventive option for women with multiple diseas e risk factors. (C) 1999 Elsevier Science Ltd. All rights reserved.