Bone Abstracts

Effective treatments are available to reduce fracture risk in patients with postmenopausal osteoporosis. Though factors have been identified that modify the effect of treatment with one or more the currently available drugs, as a rule patients will benefit more from treatment the higher their base risk of fracture. From a societal and clinical point of view it is surprising that many guidelines for postmenopausal osteoporosis do not target treatment to patients at the highest absolute risk, favouring treatment in younger over older postmenopausal women. Further, there is a real need for long-term data on efficacy of osteoporosis drugs. Their mechanism of action may well in many cases permit fairly short durations of treatment – perhaps one or two infusions in the case of zoledronic acid – followed by long periods off treatment.

As for long-term safety it is important to be aware that the harm:benefit ratio may not be constant over time. Indeed, some side effects – such as DVT or MI (raloxifene or strontium ranelate) or oesophagitis (oral bisphosphonates) - may precede any perceivable benefits whereas others may develop only with a long durations of treatment. In recent years, extension studies and real-world pharmacoepidemiology data have provided some data to fill in the gaps but uncertainty remains; perhaps especially about atypical femur fractures. Extrapolating from short term Swedish data on atypical femur fractures, excess atypical femur fractures could outweigh saved hip fractures after as little as 7 years of treatment. Danish data suggest no increase in the total number of subtrochanteric and shaft fractures (atypical and typical combined) after up to 10 years of alendronate treatment. Race and proximal femur geometry are important risk factors for atypical femur fractures so the risk will be much lower in some patients than in others. New data on bone quality using microindentation analysis find equally impaired biomechanical competence in atypical femur fractures and typical osteoporotic fractures but no impairment in long-term bisphosphonate users.

In conclusion, given the relative paucity of long-term efficacy and safety data, physicians should regularly re-assess the indication for treatment. Treatment with antiresorptive drugs for more than five years should be reserved for high risk patients only.