Bone effects of exemestane vs. tamoxifen within the TEAM trial: results of a prospective randomized bone sub study.

Abstract

Abstract Abstract #1143 Background: A prospective open label randomized multicenter trial was performed in the German TEAM Trial Group to compare the effects of the steroidal aromatase inhibitor Exemestane (EXE) and the ER agonist/antagonist Tamoxifen (TAM) on bone mineral density (BMD) and markers of bone turnover during adjuvant treatment of postmenopausal women with estrogen receptor positive breast cancer.
 Methods: 200 postmenopausal estrogen receptor positive breast cancer women
 were included in the bone substudy. Women with a history of osteoporosis or a disease or treatment known to effect bone metabolism were excluded. BMD and markers of bone turnover were assessed at baseline, after 6 and 12 months of treatment. BMD was performed using dual x-ray absorptiometry (DXA) at the lumber spine and femoral neck (FN). Marker of bone formation, PINP, bone specific alkaline phosphatase (BAP) and osteocalcin (OC) as well as bone resorption marker (ICPM) were analysed using standardised methods. Intent-to-treat analysis was performed based on 200 patients. The primary endpoint was to compare Exemestane and Tamoxifen with regard to changes from baseline to month 12 in BMD (g/cm²) in lumbar spine (integral of L1-L4). Results: 156 patients with a mean age of 61 yr. (+/- 7.3 yr.) were available for final analysis. Both groups were comparable regarding age, height, tumor grade and stage. Compared to women on Tamoxifen, who comprised an BMD increase of +0.9% and +0.9% after 6 and 12 months at the spine, women on EXE showed a decrease of -2.8% and -3.6%. Conversely, BMD at the FN showed a decrease of -2.1% and -2.2% in women on TAM while women on EXE showed a decrease of -3.4% after 6 and an increase of +1.1% after 12 months, respectivly. Bone formation and absorption was modulated in both groups. Details will be presented at the meeting.Conclusion: The results of the 12 months analysis in the TEAM Bone substudy confirm the bone protective effect of TAM at the spine while conversely the results at the FN showed a decrease. Women on EXE showed a decrease at the spine while there was a neutral effect at the FN. Futher evaluation of the 24 months data as well as the fracture rate of the total TEAM trial are nessecary to evaluate the effect of EXE on bone health. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1143.