Surgically treated osteonecrosis and osteomyelitis of the jaw and oral cavity in patients highly adherent to alendronate treatment: a nationwide user-only cohort study including over 60,000 alendronate users

Summary: Osteonecrosis of the jaw (ONJ) is rare (2.53/10,000 person-years) among alendronate users, but long-term and compliant use are associated with an increased risk of surgically treated ONJ. Risk of surgically treated ONJ is higher in patients with rheumatoid diseases and use of proton pump inhibitors. Introduction: ONJ is a rare event in users of oral bisphosphonates. Our aims were to evaluate if the risk of surgically treated ONJ increases with longer or more compliant treatment with alendronate for osteoporosis and to identify risk factors for surgically treated ONJ. Methods: Open nationwide register-based cohort study containing one nested case-control study. Patients were treatment-naïve incident users of alendronate 1996–2007 in Denmark, both genders, aged 50–94 at the time of beginning treatment (N = 61,990). Participants were followed to 31 December 2013. Results: Over a mean of 6.8 years, 107 patients received surgery for ONJ or related conditions corresponding to an incidence rate of 2.53 (95% confidence interval (CI) 2.08 to 3.05) per 10,000 patient years. Recent use was associated with an adjusted odds ratio (OR) 4.13 (95% CI 1.94 to 8.79) compared to past use. Similarly, adherent users (medication possession ratio (MPR) >50%) were at two to threefold increased risk of ONJ compared to low adherence (MPR <50%), and long-term (>5 years) use was related with higher risk (adjusted OR 2.31 (95% CI (1.14 to 4.67)) than shorter-term use. History of rheumatoid disorders and use of proton pump inhibitors were independently associated with surgically treated ONJ. Conclusions: Our data suggest that recent, long-term, and compliant uses of alendronate are associated with an increased risk of surgically treated ONJ. Nevertheless, the rates remain low, even in long-term adherent users. ONJ risk appears higher in patients with conditions likely to indirectly affect the oral mucosa.