Bone density and structure in healthy postmenopausal women treated with exemestane for the primary prevention of breast cancer: a nested substudy of the MAP.3 randomised controlled trial.

BACKGROUND: Exemestane can prevent breast cancer in postmenopausal women. Because of potential widespread use, we examined the safety of exemestane on bone health. METHODS: In this nested safety substudy of the MAP.3 trial (a randomised, placebo-controlled, double-blind trial of exemestane 25 mg a day for the primary prevention of breast cancer), we included postmenopausal women from five centres who were eligible to participate in MAP.3, not osteoporotic, not receiving drugs for bone-related disorders, with baseline lumbar spine, total hip, and femoral neck T-scores above -2·0. The primary endpoint was percent change from baseline to 2 years in total volumetric bone mineral density (BMD) at the distal radius by high-resolution peripheral quantitative CT. The primary analysis was per protocol using a non-inferiority margin. This analysis was done earlier than originally planned because of the impending announcement of MAP.3 results and subsequent unmasking of patients to treatment assignment. This study is registered with ClinicalTrials.gov, number NCT01144468, and has been extended to 5 years of unmasked follow-up. FINDINGS: 351 women (176 given exemestane, 175 given placebo; median age 61·3 years [IQR 59·2-64·9]) met our inclusion criteria and completed baseline assessment. At the time of clinical cutoff, 242 women had completed 2-year follow-up (124 given exemestane, 118 given placebo). From baseline to 2 years, the mean percent change in total volumetric BMD at the distal radius was -6·1% (95% CI -7·0 to -5·2) in the exemestane group and -1·8% (-2·4 to -1·2) in the placebo group (difference -4·3%, 95% CI -5·3 to -3·2; p<0·0001). The lower limit of the 95% CI was lower than our non-inferiority margin of negative 4% (one-sided test for non-inferiority p=0·70), meaning the hypothesis that exemestane was inferior could not be rejected. At the distal tibia, the mean percent change in total volumetric BMD from baseline to 2 years was -5·0% (95% CI -5·5 to -4·4) in the exemestane group and -1·3% (-1·7 to -1·0) in the placebo group (difference -3·7%, 95% CI -4·3 to -3·0; p<0·0001). The mean percent change in cortical thickness was -7·9% (SD 7·3) in the exemestane group and -1·1% (5·7) in the placebo group at the distal radius (difference -6·8%, 95% CI -8·5 to -5·0; p<0·0001) and -7·6% (SD 5·9) in the exemestane group and -0·7% (4·9) in the placebo group at the distal tibia (difference -6·9%, -8·4 to -5·5; p<0·0001). Decline in areal BMD, as measured by dual-energy x-ray absorptiometry, in the exemestane group compared with the placebo group occurred at the lumbar spine (-2·4% [95% CI -3·1 to -1·7] exemestane vs -0·5% [-1·1 to 0·2] placebo; difference -1·9%, 95% CI -2·9 to -1·0; p<0·0001), total hip (-1·8% [-2·3 to -1·2] exemestane vs -0·6% [-1·1 to -0·1] placebo; difference -1·2%, -1·9 to -0·4; p=0·004), and femoral neck (-2·4% [-3·2 to -1·7] exemestane vs -0·8% [-1·5 to 0·1] placebo; difference -1·6%, -2·7 to -0·6; p=0·002). INTERPRETATION: 2 years of treatment with exemestane worsens age-related bone loss in postmenopausal women despite calcium and vitamin D supplementation. Women considering exemestane for the primary prevention of breast cancer should weigh their individual risks and benefits. For women taking exemestane, regular bone monitoring plus adequate calcium and vitamin D supplementation are important. To assess the effect of our findings on fracture risk, long-term follow-up is needed. FUNDING: Canadian Breast Cancer Research Alliance (Canadian Institutes of Health Research/Canadian Cancer Society).

Effect of 12 months of whole-body vibration therapy on bone density and structure in postmenopausal women: a randomized trial.

BACKGROUND: Although data from studies in animals demonstrated beneficial effects of whole-body vibration (WBV) therapy on bone, clinical trials in postmenopausal women showed conflicting results. OBJECTIVE: To determine whether WBV improves bone density and structure. DESIGN: A 12-month, single-center, superiority, randomized, controlled trial with 3 parallel groups. (ClinicalTrials.gov registration number: NCT00420940) SETTING: Toronto General Hospital, Ontario, Canada. PARTICIPANTS: 202 healthy postmenopausal women with bone mineral density (BMD) T-scores between -1.0 and -2.5 who were not receiving prescription bone medications. INTERVENTION: Participants were randomly assigned to 1 of 3 groups (1:1:1 ratio) by using a block-randomization scheme and sealed envelopes. They were asked to stand on a low-magnitude (0.3g) 90-Hz or 30-Hz WBV platform for 20 minutes daily or to serve as control participants; all participants received calcium and vitamin D. MEASUREMENTS: Bone outcome assessors, who were blinded to group assignment, determined trabecular volumetric BMD and other measurements of the distal tibia and distal radius with high-resolution peripheral quantitative computed tomography and areal BMD with dual-energy x-ray absorptiometry at baseline and at 12 months. RESULTS: 12 months of WBV therapy had no significant effect on any bone outcomes compared with no WBV therapy. For the primary outcome of tibial trabecular volumetric BMD, mean change from baseline was 0.4 mg/cm(3) (95% CI, -0.4 to 1.2 mg/cm(3)) in the 90-Hz WBV group, -0.1 mg/cm(3) (CI, -1.0 to 0.8 mg/cm(3)) in the 30-Hz WBV group, and -0.2 mg/cm(3) (CI, -1.1 to 0.6 mg/cm(3)) in the control group (P = 0.55). Changes in areal BMD at the femoral neck, total hip, and lumbar spine were also similar among the groups. Overall, low-magnitude WBV at both 90 and 30 Hz was well-tolerated. LIMITATIONS: Adherence to WBV ranged from 65% to 79%. Double-blinding was not possible. CONCLUSION: Whole-body vibration therapy at 0.3g and 90 or 30 Hz for 12 months did not alter BMD or bone structure in postmenopausal women who received calcium and vitamin D supplementation.