DXA Monitoring After 5 Years of Bisphosphonate Therapy
After 5 years of oral bisphosphonate therapy (or 3 years of IV zoledronate), obtain a DXA scan to reassess fracture risk and determine eligibility for a drug holiday. 1, 2
Risk Stratification at 5 Years Determines Next Steps
The decision to continue therapy versus initiate a drug holiday hinges on your patient's current fracture risk status:
Consider a Drug Holiday If:
- Hip T-score is greater than -2.5 AND
- Patient has remained fracture-free AND
- No history of hip or vertebral fractures 1, 2
For these lower-risk patients, a bisphosphonate holiday of 2-5 years is appropriate, with the understanding that residual antifracture effects persist due to bisphosphonate skeletal retention 3.
Continue Treatment If High Risk:
- Hip T-score ≤ -2.5 after initial treatment period
- History of hip or vertebral fractures
- Multiple non-spine fractures
- Advanced age with frailty
- Fracture occurred during therapy
- High-dose glucocorticoid use 1, 2, 4
Continue oral bisphosphonates up to 10 years total (or IV zoledronate up to 6 years) in these high-risk patients before reassessing again 1, 3.
Monitoring During a Drug Holiday
The AACE guidelines provide clear triggers for resuming therapy 1:
- BMD decline beyond the least significant change (LSC) of your DXA machine
- New fracture occurrence
- Bone turnover markers rise to pretreatment values
- Reassess fracture risk every 2-4 years during the holiday 2, 5
A critical pitfall: bone turnover markers (particularly bone-specific alkaline phosphatase) increase significantly within 6 months of stopping bisphosphonates, with more pronounced rises in patients who subsequently fracture 5. This can serve as an early warning sign.
Important Nuances by Bisphosphonate Type
For IV zoledronate specifically: The reassessment timeline is shorter—after 3 years rather than 5 years—due to its more potent and sustained effects 1, 2. The evidence from HORIZON extension trials showed residual fracture protection after 3 years of annual infusions 3.
For oral bisphosphonates (alendronate, risedronate): The standard 5-year reassessment applies, with evidence from FLEX showing continued vertebral fracture reduction with 10 years versus 5 years of alendronate, particularly in women with hip T-scores between -2.0 and -2.5 3.
Critical Clinical Considerations
The femoral neck BMD appears more predictive than lumbar spine for determining holiday eligibility 4, 3. Real-world data shows statistically significant femoral neck BMD decline by year 2 of a drug holiday, even when lumbar spine BMD remains stable 5.
Very high-risk patients (severe/multiple vertebral fractures, very low T-scores) may warrant 6-10 years of oral bisphosphonate stability before considering any holiday 1. In these patients, the rare risks of atypical femoral fractures and osteonecrosis of the jaw—which increase with duration beyond 5 years 6, 3—are outweighed by vertebral fracture risk reduction.
What NOT to Do
Never initiate a drug holiday without obtaining a DXA scan first to document current BMD status. The hip T-score is your primary decision point 1, 2.
Do not apply drug holiday concepts to denosumab—it requires continuous therapy or transition to another antiresorptive due to rapid rebound bone loss and increased fracture risk upon discontinuation 1, 2.