Monitoring
The aim of monitoring the therapy is to increase treatment adherence and to verify response to therapy, including the presence of new fractures or new risk factors and tolerability and adverse effects of treatment. The benefits of bone loss prevention are persistent with continued treatment but disappear with medication cessation. The BMD decreases within 1-2 years of stopping therapy, and bone turnover markers return to pretreatment levels after a few months.
Bone Mineral Density (BMD) Measurement
Bone mineral density measurement is recommended every 1-2 years after initiation of therapy until findings are stable and every 1-3 years thereafter. The BMD measurement done while on treatment correlates with the patient's current fracture risk. Central DXA of the spine or hip is the gold standard for serial bone mineral density assessment and should be done every 2 years. If the spine, hip, or both cannot be assessed, the 33% radius site can be used. Patient follow-up ideally should be done within the same facility using the same machine. Age-, disease-, and treatment-related BMD changes can be monitored using QCT measurement of trabecular bone mineral density.
Bone Turnover Markers
Bone resorption markers (eg fasting serum C-terminal crosslinking telopeptide of type I collagen) may be measured before starting therapy and 3 or 6 months after starting treatment. Bone formation markers (eg serum procollagen type I N-terminal propeptide) may be measured before starting therapy and 6 months later. High levels of bone resorption markers are associated with an increased risk of osteoporotic fractures. Resorption markers may be used for assessing fracture risk in selected patients when BMD and clinical risk factors are not sufficient to make treatment decisions.
Vertebral Imaging
Repeat vertebral imaging is indicated for patients with the following: Documented height loss; presence of vertebral pain; changes in posture; chest X-ray abnormalities; due for re-evaluation of treatment with possible withdrawal of therapy; and the presence of vertebral fracture during the off-treatment interval.
Reassessment of Postmenopausal Women on Long-Term Bisphosphonate Therapy
Postmenopausal women who have been taking oral bisphosphonates for ≥5 years or IV bisphosphonates for ≥3 years should be reassessed for the presence of fractures prior to initiation and during therapy. Bisphosphonate therapy can be continued beyond 3-5 years in patients ≥75 years old on high-dose oral glucocorticoid treatment, with a prior history of hip or vertebral fracture, or who sustained a low-trauma fracture during therapy. If fractures occur, treatment with bisphosphonates may be continued, or the use of other agents may be considered. If fracture-free, assess bone mineral density T-score or fracture risk. If with a hip BMD T-score of ≤-2.5 or with high fracture risk, consider continuing bisphosphonate therapy or changing to other alternative agents. If with normal bone mass and still no fractures, may consider withholding treatment and advise the patient to follow up every 2-3 years.
Monitoring Therapy in Men with Osteoporosis
Patients can be monitored with bone mineral density measurements as recommended for postmenopausal women. There may be limitations to the use of spine DXA in aging men due to interference from osteophytes and vascular calcifications on the spine measurement.
Treatment Failure
Treatment failure is defined as (after excluding secondary osteoporosis or maximal treatment adherence) ≥2 incident fragility fractures; one incident fracture and elevated serum CTX or P1NP at baseline with no significant reduction during treatment or a significant decrease in BMD or both; or no significant decrease in serum CTX or P1NP but a significant decrease in bone mineral density. Treatment modifications may include replacing a weaker antiresorptive agent with a more potent one from the same class, replacing an oral drug with an injectable one, or replacing a strong antiresorptive agent with an anabolic agent. Evaluate the patient's adherence to therapy and address factors associated with poor treatment adherence, eg inadequate patient or caregiver education and presence of adverse events.
Specialist Referral
Consider referral to a specialist if: Multiple fragility fractures and/or subsequent fragility fractures are experienced; a non-major trauma fracture is sustained by a patient with normal bone mineral density; continued bone loss or recurrent fractures happen in a patient on therapy but have no clear causes of bone loss that are treatable; osteoporosis has uncommon features, is severe, or rare secondary conditions are present, eg hyperparathyroidism, increased prolactin; a condition is present that makes management difficult, eg chronic kidney disease, malabsorption, and high-dose glucocorticoid treatment.