Effect of tamoxifen and transdermal hormone replacement therapy on cardiovascular risk factors in a prevention trial

The combination of tamoxifen and transdermal hormone replacement therapy (HRT) may potentially reduce risks and side-effects of either agent, but an adverse interaction could attenuate their beneficial effects. We assessed the effects of their combination on cardiovascular risk factors within a prevention trial of tamoxifen. Baseline and 12-month measurements of total, low-density lipoprotein (LDL) and high-density lipoprotein (HDL)-cholesterol, platelets and white blood cells were obtained in the following four groups: tamoxifen (n = 1117), placebo (n = 1112), tamoxifen and HRT (n = 68), placebo and HRT (n = 87). The analysis was further extended to women who were on HRT at randomization but discontinued it during the 12-month intervention period (n = 33 on tamoxifen and n = 35 on placebo) and to women who were not on HRT but started it during intervention (n = 36 in both arms of the study). Compared with small changes in the placebo group, tamoxifen was associated with changes in tot...