Effect of exemestane on bone turnover markers and bone mineral density (BMD): 2 year results of the Dutch/Belgian Tamoxifen Exemestane Adjuvant Multicentre (TEAM) trial.

Abstract

#1154 Background Aromatase inhibitors (AIs) given to women with early breast cancer may adversely affect bone metabolism. We studied the effect of exemestane (E) on bone mineral density (BMD) and bone turnover and compared it to the effect of tamoxifen (T) treatment in a group of women participating in the Dutch and Belgian Tamoxifen Exemestane Adjuvant Multicentre (TEAM) trial. In this trial, postmenopausal women with hormone sensitive early breast cancer (n=3168) were randomised between 5 years E or 2½-3 years T followed by 2½-2 years of E.
 Methods In this subprotocol, 87 women were followed for two years. Patients with bone diseases were excluded. Total hip and lumbar spine BMD were assessed at baseline and after 1 and 2 years. The bone resorption marker cross-linked telopeptide of type-I collagen (CTX) and the bone formation marker N-terminal propeptide of type I collagen (PINP) were measured in fasting serum at baseline and after 3, 6, 12 and 24 months.
 Results At baseline, there was no difference in total hip (E: 0.85g/cm2, T: 0.80g/cm2; p=0.642) and lumbar spine BMD (E: 0.99g/cm2, T: 1.02g/cm2; p=0.545) between both groups. After 2 years, there were no significant changes in total hip BMD (E: 0.02 g/cm2 95%CI -0.05;0.08, p=0.849; T: 0.03 g/cm2, 95%CI -0.02;0.09, p=0.466) and in spine BMD (E: -0.02 g/cm2 95%CI -0.11;0.06, p=0.834; T: 0.02 g/cm2 95%CI -0.05;0.10, p=0.747). At baseline, there was no difference in serum CTX (E: 0.34ng/mL, T: 0.29ng/mL; p=0.271) and P1NP (E: 57ng/L, T:58ng/L, p=0.973) between both groups. After 2 years of treatment, serum CTX increased, although not significantly in the E group (20%, 95%CI -6%;54%, p=0.223) while it decreased significantly in the T group (-40%, 95%CI -23%;-53%, p<0.001). At 24 months, the CTX was 0. 44ng/mL (E) and 0. 18ng/mL (T). Serum P1NP did not change in the E group (-2%, 95%CI -20%;19%, p=0.837) but decreased significantly in the T group (-48%, 95%CI -36%;-58%, p<0.001). At 24 months, the P1NP was 55ng/L (E) and 28ng (T).
 Conclusion Although there was a trend for an increase in bone resorption with E treatment, this was not significant and was not associated with a decrease in BMD. The magnitude of the reported negative effect of aromatase inhibitors on bone metabolism in studies using T as comparator treatment may be overestimated by the effect of T on bone turnover. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1154.