Osteoporosis and rate of bone loss among postmenopausal survivors of breast cancer - Results from a subgroup in the women's health initiative. Observational study

BACKGROUND. Breast cancer diagnosis and treatment may put women at higher risk for osteoporosis in later life. METHODS. in a subgroup of participants in the Women's Health Initiative Observational Study, authors of the current study investigated differences in bone mineral density (BMD, measured by dual-energy x-ray absorptiometry) between breast cancer survivors (n = 209) and a noncancer reference group (n = 5759). RESULTS. in comparison to the reference group, breast cancer survivors had significantly lower total body BMD value (0.989 vs. 1.013 g/cm(2), p = 0.001) and total hip BMD value (0.823 vs. 0.845 g/cm(2), p = 0.02) at baseline after adjustment for age, race/ethnicity, years since menopause, and clinical center. These lower BMD levels were largely explained by lower usage of hormone therapy (HT) among survivors: after additional statistical adjustment for HT, hip BMD values were 0.834 versus 0.844 g/cm(2) (p = 0.26), and total body values were 1.005 versus 1.013 g/cm(2)(P = 0.33) for survivors and reference women, respectively. More than 77% of survivors with osteoporosis were undiagnosed by their healthcare providers, and this was similar to the undiagnosed rate in the reference group (85.7%). Longitudinally, breast cancer survivors in this study did not demonstrate an accelerated rate of bone loss compared with the reference population. CONCLUSIONS. Associated with lower HT usage, postmenopausal survivors of breast cancer were more likely to have low BMD in comparison to other women of the same age; and many of these survivors with osteoporosis were undiagnosed.