Reversal of skeletal effects of endocrine treatments in the intergroup exemestane study.

Abstract #1128 The Intergroup Exemestane Study (IES) has demonstrated significantly improved disease related outcomes for post-menopausal women with ER+/unknown early breast cancer who switch to exemestane (E) after 2-3 years pre-treatment with tamoxifen (T). In comparison to 5 years T, a switch to E is associated with a favorable adverse event profile other than an increase in musculoskeletal side effects, accelerated bone loss & increased fracture incidence. Here we report effects of endocrine treatment withdrawal on bone mineral density (BMD) at lumbar spine (LS) & total hip (TH), bone turnover markers (BTM) & fracture rates.
 Of the 4724 patients (pts) who took part in IES, 206pts (101E, 105T) at selected centres with no evidence of osteoporosis or osteoporotic fracture were included in a bone health substudy. BMD & BTM were assessed pre-randomization, after 6, 12, & 24 months (m) treatment, end of treatment (EOT), 12 & 24m post EOT. BTM were also assessed after 3, 9, 18, 30 & 3m post EOT. To evaluate treatment withdrawal effects, 12 & 24m post EOT BMD results are available for 160 (76E, 84T) & 159 (75E, 84T) pts respectively. Similar pt numbers also had BTM (urinary NTX & DPD, serum CTX, bone ALP, osteocalcin & PICP) measured post EOT.
 At EOT an ITT analysis showed that the switch to E was associated with a -3.9% & -3.0% reduction since randomization in LS & TH BMD respectively, compared with -1.2% &-1.6% for continuing on T, resulting in an EOT difference between mean E & T BMD of 2.8% (p= Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1128.