Prevention of osteoporosis and uterine effects in postmenopausal women taking raloxifene for 5 years

Abstract

Objective: Raloxifene hydrochloride (60 mg/day) is a selective estrogen receptor modulator indicated for the prevention and treatment of postmenopausal osteoporosis. Raloxifene treatment for 3 years increases bone mineral density (BMD) and, unlike tamoxifen (a triphenylethylene selective estrogen receptor modulator), does not stimulate the endometrium in healthy postmenopausal women. The effect of longer duration of treatment with raloxifene is not known. Therefore, the main objectives of these analyses are (1) to compare the effect of 5 years of treatment with raloxifene (60 mg/day) with placebo in terms of the likelihood of developing osteoporosis and (2) to evaluate the effect of 5 years of raloxifene treatment on the endometrium and incidence of vaginal bleeding.

Design: The current analyses include integrated data from two identically designed, prospective, double-blinded trials including postmenopausal women (mean age, 55 years) randomly assigned to either placebo (n = 143) or raloxifene (60 mg/day; n = 185). Osteoporosis and osteopenia were diagnosed according to World Health Organization criteria, using the manufacturer's database for the lumbar spine and the National Health and Nutrition Examination Survey's 1998 reference base for the hip. Endometrial thickness was determined using transvaginal ultrasonography. Clinical diagnoses of endometrial hyperplasia or endometrial cancer were confirmed by blinded review of histopathology reports.

Results: Compared with the case of placebo, raloxifene treatment for 5 years reduced bone turnover markers (osteocalcin: -10.9%, P < 0.001; bone-specific alkaline phosphatase: -7.2%, P = 0.042; urinary C-telopeptide: -11.1%, P = 0.034) and was associated with increased BMD in the lumbar spine (2.8%; P < 0.001) and total hip BMD (2.6%; P < 0.001). Women taking raloxifene were less likely to develop osteoporosis (relative risk [RR] for raloxifene v placebo: 0.13; 95% CI: 0.00, 0.37; P = 0.001) or osteopenia (RR: 0.23; 95% CI: 0.00, 0.81; P = 0.038) at the lumbar spine and were more likely to convert to normal BMD status at the lumbar spine (RR: 4.01; 95% CI: 1.34, 11.23; P = 0.043) and total hip (RR: 3.92; 95% CI: 1.12,14.27; P = 0.011) at 5 years, compared with the case of placebo. Raloxifene also significantly reduced total cholesterol (-5.5%; P < 0.001) and low-density lipoprotein cholesterol (-8.7%; P < 0.001), compared with the case of placebo. No significant changes in high-density lipoprotein cholesterol (P = 0.257) or triglycerides (P = 0.620) were detected. Incidence of hot flashes was higher among women taking raloxifene compared with those taking placebo [raloxifene, 47 (28.8%); placebo, 21 (16.8%); P = 0.017]. Women taking placebo or raloxifene reported a similar incidence of vaginal bleeding (P = 0.999) or of mean endometrial thickness of more than 5 mm at baseline and at each visit, up to the 5-year endpoint (P >/= 0.349). No diagnoses of endometrial hyperplasia or endometrial cancer were made in either treatment group.

Conclusions: Five years of raloxifene treatment in healthy postmenopausal women preserves BMD, significantly reduces the likelihood of development of osteoporosis, and was not associated with an increased rate of vaginal bleeding, endometrial hyperplasia, or endometrial carcinoma, compared with the case of placebo.