Treatment responses with once-weekly teriparatide therapy for osteoporosis

Monitoring bone mineral density is useful to assess treatment response for osteoporosis, but it does not always reflect fracture prevention. Two types of bone mineral density thresholds were used to analyze data from a once-weekly teriparatide trial, and they appear to be useful indicators of treatment success for osteoporosis.

This study aimed to clarify whether the criteria of treatment response could be used to evaluate treatment success with once-weekly teriparatide.

The data of subjects whose lumbar or femoral neck bone mineral density (BMD) was measured in the TOWER study were included. The least significant change (LSC) and the absolute change were used as the criteria for judgment of treatment success. The correlation between the incidence of fractures and the treatment response was also assessed.

There was no significant difference in baseline characteristics between the placebo and teriparatide groups. Once-weekly teriparatide therapy for 72 weeks showed treatment success in 79.2 % of the subjects for lumbar BMD and 44.1 % for femoral neck BMD by LSC and in 50.5 and 39.6 % by absolute change, respectively. A lower incidence of vertebral fracture was observed in patients who achieved treatment success for lumbar BMD. With the LSC, some treatment success was observed in the early phase of treatment, and it increased with treatment duration.

It appears that the LSC could be used as a surrogate efficacy indicator at an earlier stage of treatment, and the absolute criterion of -2.5SD was confirmed as a useful marker of long-term treatment success.