Raloxifene reduces risk of vertebral fractures and breast cancer in postmenopausal women regardless of prior hormone therapy

Objective We examined whether past use of hormone therapy influences the effects of raloxifene on the risk of new vertebral fracture, cardiovascular events, or breast cancer. Study Design The Multiple Outcomes of Raloxifene Evaluation (MORE) trial examined vertebral fracture incidence as the primary endpoint, breast cancer incidence as a secondary endpoint. Cardiovascular events were collected as secondary safety endpoints. Population: The MORE trial enrolled 7705 postmenopausal women. Of the 7682 women who reported their previous HT use status, 29% used HT before screening. Outcomes Measured Separate logistic regression models analyzed the relationships between prior HT use and the risk of vertebral fracture, cardiovascular events, or breast cancer. Interaction terms with P<.10 were considered to be statistically significant. Confidence intervals for relative risks (RR) were calculated using the Mantel-Haenszel method. Results Raloxifene 60 mg/d, the clinically approved dose for osteoporosis prevention and treatment, reduced the risk of vertebral fractures by 54% (RR=0.46) and 29% (RR=0.71) in women with and without prior HT use, respectively (interaction P=.05). A lower incidence of invasive breast cancer in women with prior HT use (RR=0.23) and in women without prior HT use [RR=0.31; interaction P=.60] was observed in women receiving raloxifene (pooled doses). Irrespective of prior HT use, women treated with raloxifene (pooled doses) had no change in incidence of cardiovascular events (interaction P=.56). Conclusions: The risk of vertebral fractures was lower in women treated with raloxifene, regardless of prior HT use, but there was a suggestion that the effect was greater in women who had used HT. Women randomized to receive raloxifene exhibited a decreased incidence of invasive breast cancer, compared with women receiving placebo. No change occurred in the incidence of cardiovascular events, regardless of prior HT use.