Objective: Bisphosphonate treatment does not increase bone mineral density (BMD) in all subjects particularly at the femoral neck (FN). Our aim was to evaluate the relationship between response to oral bisphosphonate (oBP) at the FN and change in BMD following discontinuation.
Methods: Data were collected retrospectively from postmenopausal women on oBP for ≥3 years, attending a real-world metabolic clinic at initiation of oBP, discontinuation, and 1 to 2 years post discontinuation. Improvement in BMD ≥4% in the FN and ≥5% for the lumbar spine (LS) were deemed clinically meaningful and used as least significant change (LSC) values. We divided subjects based on FN BMD response and compared outcomes between responders and non-responders after oBP discontinuation.
Results: Of the 213 subjects, 32.1% showed an increase ≥LSC at the FN compared to 57.1% at the LS on treatment (P < .0001). FN responders had lower BMD levels at pretreatment baseline than non-responders both at the FN (0.58 vs 0.62 g/cm2; P = .003) and LS (0.76 vs 0.79 g/cm2; P = .044). Off-treatment, more subjects lost BMD ≥LSC at FN in the responder group than in the non-responder group (37.5% vs 14.2%; P < .001). BMD remained above pre-treatment levels in responders after a median follow-up of 1.52 years.
Conclusion: BMD response at FN is suboptimal in patients on oBP and is much less common than LS response. FN responders tend to lose the accumulated bone quickly off-treatment, though BMD remains above pretreatment levels. These observations suggest that new approaches may be needed to optimize osteoporosis management in real-world patients.
Keywords: bisphosphonate; bone mineral density; drug holiday; treatment response.
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