Bone mineral density (BMD) is used to assess the efficacy of bisphosphonate treatment in the individual patient, however it is unclear whether the response rate is similar for all oral bisphosphonates. The TRIO study is a randomised, open-label, parallel, controlled trial of three bisphosphonates, orally administered at their licensed dose for two years. We recruited postmenopausal women (n=172, ages 53-84 years) with a BMD T-score, by DXA, of <-2.5 at the spine and/or total hip, or of <-1.0 plus a previous low trauma fracture. Women were randomised to receive one of three bisphosphonates, either alendronate 70 mg once weekly, risedronate 35 mg once weekly, or ibandronate 150 mg once monthly, together with calcium (1200 mg) and vitamin D (800 IU) daily supplements. Lumbar spine and total hip BMD were measured at baseline and weeks 12 (in duplicate), 48 and 96. We calculated changes in lumbar spine and total hip BMD between baseline and weeks 12, 48 and 96 for each individual. The duplicate week 12 results were used to calculate the least significant change (LSC) for lumbar spine (4.4%) and total hip BMD (4.2%). Women could be classified as treatment responders if their individual BMD increase was greater than the site-specific LSC. Differences in the number of responders by weeks 12, 48 and 96 were examined using chi-squared tests (Table 1). Even though the LSCs were similar, lumbar spine BMD was able to identify more treatment responders than total hip BMD. We found that the number of treatment responders was dependent on the bisphosphonate type. By week 96, more women had responded to alendronate than ibandronate and risedronate.
|Week 12||Week 48||Week 96|
|Proportion of responders (n/group n)||Responders (%)||Proportion of responders (n/group n)||Responders (%)||Proportion of responders (n/group n)||Responders (%)|
|Number of responders is significantly different between bisphosphonates by chi-squared testing; a (p=0.02), b (p=0.002) and c (p=0.02).Number of responders is significantly different between bisphosphonates by chi-squared testing; a (p=0.02), b (p=0.002) and c (p=0.02).|
Disclosure: The authors declared no competing interests. This work was funded by Warner Chilcott.