The predictive value of bone turnover markers during discontinuation of alendronate: the PROSA study

Bisphosphonate drug holidays in osteoporosis according to fracture risk profile

We analyzed the incidence of fractures and changes in bone mineral density and bone turnover markers in 264 patients who discontinued bisphosphonates. Fractures were recorded in 12.3%. Half were clinical vertebral fractures. We identified patients with a high-risk profile who should not discontinue treatment.

OBJECTIVE

The optimal length of bisphosphonate discontinuation is unknown, as is the type of patient who could benefit from this approach. The objectives of the study were to analyze, in clinical practice, the incidence of fractures and associated risk factors, changes in bone mineral density (BMD) and bone turnover markers (BTMs) after discontinuation of bisphosphonates.

METHODS

This observational retrospective study included 264 patients from 14 Spanish rheumatology departments. Postmenopausal women or men with osteoporosis received alendronate or risedronate for ≥ 5 years or zoledronate for ≥ 3 years and had discontinued treatment for ≥ 1 year or ≥ 2 years, respectively. Spinal X-rays were obtained before discontinuation and in suspected clinical vertebral fracture during follow-up. BMD and BTMs were determined before discontinuation and at different time points.

RESULTS

The mean discontinuation time was 2.7 (± 6.7) years. Thirty-two patients (12.3%) had 36 fractures, mainly clinical vertebral fractures. The main risk factor for fracture was a high-risk profile (femoral neck T-score ≤ -2.5 and/or a history of fracture and/or multiple fractures [≥ 5 years]) before discontinuation. At 12 months, 10.41% of patients with high-risk profile experienced a fracture, being 0.8% and 1.08% in moderate- and low-risk patients, respectively. Significant BMD loss at the femoral neck and total hip was detected, with duration of discontinuation being the key factor. PINP was the marker with the greatest changes.

CONCLUSIONS

We identified a profile of patients with osteoporosis who should not discontinue bisphosphonates, owing to the possibility of fractures, especially vertebral, which are already evident the first year after discontinuation.

Effect of Oral Bisphosphonate Drug Holiday on Mortality Following Hip Fracture

CONTEXT

Current clinical guidelines recommend a drug holiday after extended use of oral bisphosphonates. However, no studies have investigated the effect of drug holidays before hip fractures on postfracture mortality.

OBJECTIVE

This work aimed to investigate the effect of a drug holiday on postfracture mortality in patients with extended use of oral bisphosphonates.

METHODS

This retrospective, population-based cohort study took place among all patients with hip fractures in Victoria, Australia, from 2014 to 2018. Patients were adherent to oral alendronate or risedronate for 5 years or more prior to hip fracture. Group-based trajectory modeling categorized patients into different bisphosphonate usage after 5-year good adherence. The main outcome measure was postfracture mortality.

RESULTS

We identified 365 patients with good adherence (medication possession ratio ≥80%) to oral alendronate/risedronate for 5 years or more. Most patients (69%) continued to use oral bisphosphonates until admission for hip fracture; 17% had discontinued for 1 year and 14% had discontinued for 2 years. Postfracture mortality was higher in patients who had discontinued risedronate for 1 year (hazard ratio [HR] 2.37; 95% CI, 1.24-4.53) and 2 years (HR 3.08; 95% CI, 1.48-6.41) prior to hip fracture. No increase or decrease in postfracture mortality was observed in patients who had discontinued alendronate for 1 year (HR 0.59; 95% CI, 0.29-1.18) or 2 years (HR 1.05; 95% CI, 0.57-1.93) prior to hip fracture.

CONCLUSION

Postfracture mortality is higher in people who discontinue risedronate, but not alendronate, for 1 or 2 years after being adherent to treatment for at least 5 years. The type of bisphosphonate may be a factor to consider when planning drug holidays.

Current use of bone turnover markers in the management of osteoporosis

The adult bone is continuously being remodelled to repair microdamage, preserve bone strength and mechanical competence as well as maintain calcium homeostasis. Bone turnover markers are products of osteoblasts (bone formation markers) and osteoclasts (bone resorption markers) providing a dynamic assessment of remodelling (turnover). Resorption-specific bone turnover markers are typically degradation products of bone collagen molecules (N- [NTX] and C-telopeptide cross-linked type 1 collagen [CTX]), which are released into the circulation and excreted in urine; or enzymatic activities reflecting osteoclastic resorption, tartrate-resistant acid phosphatase [TRACP]. Formation-specific bone turnover markers embrace different osteoblastic activities: type 1 collagen synthesis (Procollagen type I N- propeptide [PINP]), osteoblast enzymes (bone-specific alkaline phosphatase [BALP]), or bone matrix proteins [osteocalcin]. Among individuals not receiving osteoporosis treatment, resorption and formation markers are tightly linked and highly correlated (r= 0.6-0.8). Significant biological variability was reported in the past, but these issues have been greatly improved with automated assays and attention to pre-analytical and analytical factors that are known to influence bone turnover marker levels. Bone turnover markers are not useful in the diagnosis of osteoporosis, the individual prediction of bone loss, fracture, or rare complications, or in the selection of pharmacological treatment. Despite remaining issues with reference intervals and assays harmonization, bone turnover markers have proven to be useful in elucidating the pharmacodynamics and effectiveness of osteoporosis medications in clinical trials. As an alternative to BMD testing, BTMs may be useful to monitor osteoporosis therapies.

Comparative Fracture Risk During Osteoporosis Drug Holidays After Long-Term Risedronate Versus Alendronate Therapy : A Propensity Score-Matched Cohort Study

BACKGROUND

An osteoporosis drug holiday is recommended for most patients after 3 to 5 years of therapy. Risedronate has a shorter half-life than alendronate, and thus the residual length of fracture protection may be shorter.

OBJECTIVE

To examine the comparative risks of drug holidays after long-term (≥3 years) risedronate versus alendronate therapy.

DESIGN

Population-based, matched, cohort study.

SETTING

Province-wide health care administrative databases providing comprehensive coverage to Ontario residents aged 65 years or older between November 2000 and March 2020.

PATIENTS

Persons aged 66 years or older who had long-term risedronate therapy and a drug holiday were matched 1:1 on propensity score to those who had long-term alendronate therapy and a drug holiday.

MEASUREMENTS

The primary outcome was hip fracture within 3 years after a 120-day ascertainment period. Secondary analyses included shorter follow-up and sex-specific estimates. Cox proportional hazards models were used to estimate hazard ratios (HRs) for fracture risk between groups.

RESULTS

A total of 25 077 propensity score-matched pairs were eligible (mean age, 81 years; 81% women). Hip fracture rates were higher among risedronate than alendronate drug holidays (12.4 and 10.6 events, respectively, per 1000 patient-years; HR, 1.18 [95% CI, 1.04 to 1.34]; 915 total hip fractures). The association was attenuated when any fracture was included as the outcome (HR, 1.07 [CI, 1.00 to 1.16]) and with shorter drug holidays (1 year: HR, 1.03 [CI, 0.85 to 1.24]; 2 years: HR, 1.14 [CI, 0.96 to 1.32]).

LIMITATION

Analyses were limited to health care administrative data (potential unmeasured confounding), and some secondary analyses contained few events.

CONCLUSION

Drug holidays after long-term therapy with risedronate were associated with a small increase in risk for hip fracture compared with alendronate drug holidays. Future research should examine how best to mitigate this risk.

PRIMARY FUNDING SOURCE

Canadian Institutes of Health Research.

Role of Bone Turnover Markers in Osteoporosis Therapy

Bone turnover markers fill a clinical need that improves comprehensive care of metabolic bone health and osteoporosis. Creating a standard process for drawing them that reduces modifiable variability improves their precision and clinical usefulness. Creating a standard process for interpreting them by applying statistical significance improves their clinical applicability. Understanding what causes them to increase and decrease can help elucidate secondary causes of osteoporosis. Monitoring them can assess patient adherence to therapy for a silent disease that will progressively become louder with an aging global population.

Duration of Bisphosphonate Drug Holidays in Osteoporosis Patients: A Narrative Review of the Evidence and Considerations for Decision-Making

Bisphosphonates are first-line therapy for osteoporosis, with alendronate, risedronate, and zoledronate as the main treatments used globally. After one year of therapy, bisphosphonates are retained in bone for extended periods with extended anti-fracture effects after discontinuation. Due to this continued fracture protection and the potential for rare adverse events associated with long-term use (atypical femoral fractures and osteonecrosis of the jaw), a drug holiday of two to three years is recommended for most patients after long-term bisphosphonate therapy. The recommendation for a drug holiday up to three years is derived primarily from extensions of pivotal trials with alendronate and zoledronate and select surrogate marker studies. However, certain factors may modify the duration of bisphosphonate effects on a drug holiday and warrant consideration when determining an appropriate time off-therapy. In this narrative review, we recall what is currently known about drug holidays and discuss what we believe to be the primary considerations and areas for future research regarding drug holiday duration: total bisphosphonate exposure, type of bisphosphonate used, bone mineral density and falls risk, and patient sex and body weight.