Incidence and associated factors of medication-related osteonecrosis of the jaw in breast cancer patients with bone metastases: a nationwide registry study in Finland

Abstract Objectives This study evaluated the incidence of MRONJ and associated factors among breast cancer patients with bone metastases in Finland. Materials and methods This retrospective cohort study included all adult patients with breast cancer and bone metastases who were prescribed antiresorptive therapy between 2013 and 2015. Patients were identified from national health care registers and followed through 2020. The outcome variable was MRONJ (M87.1). Covariates included age, oral diseases, dental procedures, type of antiresorptive (AR) prescribed, comorbidities, and concomitant medications. Results A total of 652 patients met the inclusion criteria. The incidence of MRONJ ranged from 0% to 2.2% among bisphosphonate users, compared with 12.6% among denosumab users and 15.3% among patients receiving sequential bisphosphonate and denosumab therapy. Both denosumab monotherapy and sequential bisphosphonate-denosumab therapy were associated with substantially increased MRONJ risk compared with bisphosphonate therapy. Conclusions Denosumab use and infection-related invasive dental procedures showed the strongest associations with MRONJ in this study population. Clinical relevance MRONJ incidence differed by type of antiresorptive therapy, with higher occurrence among patients using denosumab or bisphoshonates followed by denosumab compared with bisphosphonates. MRONJ was more frequent among patients who underwent infection-related invasive dental procedures.