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Abstract
Objective:
To evaluate fracture risk and bone mineral density (BMD) in patients with primary osteoporosis, 1 year after completing 72 weeks of weekly teriparatide injections.
Research design and methods:
After 72 weeks of teriparatide injections or placebo (original trial), treatment was unblinded and subjects were subsequently treated with bisphosphonates or other therapeutic regimens at the discretion of their physicians and followed for 1 year. Spine radiographs and BMD measurements at the lumbar spine, femoral neck, and total hip by dual energy X-ray absorptiometry were performed.
Main outcome measure:
Incident vertebral fracture rate.
Results:
A total of 465 patients were enrolled and 447 (96.1%) completed the study. In the 1 year follow-up period, new morphometric vertebral fractures occurred in 7/203 (3.4%) in the post-teriparatide group and 33/241 (13.7%) in the post-placebo group (relative risk [RR]: 0.23, 95% confidence interval [CI]: 0.10 to 0.52, P < 0.05). The cumulative incidences from the start of the original trial were 4.9% and 22.8%, respectively (RR: 0.18, 95% CI: 0.09 to 0.36, P < 0.05). There were no significant differences in incidences of vertebral fractures between subsequent therapeutic regimens in the post-teriparatide group. In subjects treated with bisphosphonates, mean BMD values further significantly increased by 9.6%, 2.9%, and 4.1% at the lumbar spine, femoral neck, and total hip, respectively (P < 0.05).
Conclusions:
The reduced risk of vertebral fracture was sustained for 1 year after completion of 72 weeks of weekly teriparatide injections. The effects did not differ between subsequent therapeutic regimens. BMD gains continued with sequential bisphosphonate treatment, but not with the other sequential therapeutic regimens. Bisphosphonates seem to be a useful choice as a subsequent treatment to weekly teriparatide.
Limitation:
This study was an observational follow-up study and the regimens of subsequent medication after discontinuation of the original TOWER trial were not randomly allocated.
Transparency
Declaration of funding
This study was supported by the Asahi Kasei Pharma Corporation.
Declaration of financial/other relationships
T.S. received research grants and consulting fees from Asahi Kasei Pharma and Daiichi Sankyo. M.S. received consulting fees from Chugai, Daiichi Sankyo, Asahi Kasei Pharma, Teijin, and MSD. M.I. has received research grants and consulting fees or other remuneration from Chugai, Daiichi Sankyo, JT, and Asahi Kasei Pharma. M.F. has received consulting fees from Astellas and Asahi Kasei Pharma. H.H. received research grants and consulting fees from Asahi Kasei Pharma, Chugai, Astellas, Ezai, Takeda, and MSD. T.N. received research grants and/or consulting fees from Chugai, Teijin, Asahi Kasei Pharma, and Daiichi Sankyo. T.K. is an employee of Asahi Kasei Pharma Corporation. Te.N., H.K. and Te.S. have disclosed that they have no significant relationships with or financial interests in any commercial companies related to this study or article.