The need for DXA assessment of breast cancer patients following 5 years tamoxifen prior to starting an aromatase inhibitor.

Abstract #6141 Introduction: Aromatase inhibitors are increasingly being used in the adjuvant treatment of post-menopausal women with breast cancer. They are more effective than tamoxifen in terms of disease free survival and have a different side effect profile, all causing loss of bone mineral density. They can be introduced at different points in the adjuvant pathway. It has been postulated that if given in the extended setting, letrozole after 5 yrs tamoxifen, bone health may be less important. Tamoxifen is reported to increase bone mineral density so should make subsequent bone mineral density reduction with letrozole less significant. The aim of this study was to determine whether DXA scanning should be undertaken in women following 5 yrs of tamoxifen prior to starting letrozole.
 Method: 166 women who had completed 5 years of tamoxifen underwent DXA with assessment of vertebral morphometry and risk factors associated with osteoporosis and fracture rate.
 Results: Mean age was 63yrs (standard deviation [S.D] 10yrs); 154 women were post menopausal being at least 2 years after their last menstrual period; 12 women were unable to recall when they menopaused. Mean t-score and S.D was calculated at each site; spine -1.26(1.3); femoral neck -1.16(1.1) and total hip -0.91(1.1). Results were categorised by lowest t-score.
 Conclusion: We have demonstrated that of 166 women following completion of 5 yrs tamoxifen 26.5% have osteoporosis and 35.5% osteopenia. 28% required treatment with bisphosphonates. It cannot be assumed that Tamoxifen will cause a sufficient increase in BMD to render DXA scanning unnecessary. All patients should have DXA scanning following completion of 5 yrs tamoxifen prior to commencing letrozole. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6141.