What predicts early fracture or bone loss on bisphosphonate therapy?

Factors predicting early fracture or bone loss on bisphosphonate therapy are not well defined. We studied 1588 patients over the age of 50 yr who were started on cyclic etidronate (1119) or alendronate (469) in the CANDOO (Canadian Database for Osteoporosis and Osteopenia Patients) Study. Incident fracture within 2 yr of starting therapy occurred in 31 patients and was independently predicted by a previous history of nonvertebral fracture (odds ratio [OR], 2.98, 95% confidence interval [CI], 1.30, 6.83, p = 0.010). Two hundred and fifty-seven patients lost >/=3% bone mass at the hip or spine (early bone loss) while on bisphosphonate therapy. Protection from early bone loss was most strongly independently predicted by treatment with alendronate with no previous history of etidronate use (OR, 0.29, CI, 0.13, 0.62, p = 0.002). In conclusion, early fracture on bisphosphonate therapy is most strongly predicted by a previous history of fracture and early bone loss is most strongly predicted by the potency of the prescribed bisphosphonate.