Medication-Related Osteonecrosis of the Jaw in Breast Cancer Patients: A Longitudinal Swedish Study of Oral Health and Antiresorptive Use

Background Breast cancer is one of the most common cancers among women, with improved therapies reducing mortality. Antiresorptive (AR) therapy is crucial for managing bone loss and skeletal complications in patients with cancer. However, high-dose AR therapy may carry a significant risk of medication-related osteonecrosis of the jaw (MRONJ). This study aims to investigate the incidence of MRONJ and its risk factors in patients with diagnosed breast cancer undergoing either biannual postoperative bisphosphonate therapy or high-dose AR therapy.Methods This study followed 220 female patients receiving AR therapy in Västra Götaland, Sweden, from 2015 to 2020. Oral health status was assessed before and during AR therapy, collecting data on the incidence of MRONJ, dental procedures, and data on breast cancer characteristics. Statistical analyses, including Kaplan-Meier survival analysis and Fisher's exact tests, identified significant trends (p < 0.05).Results The cohort comprised 119 patients on biannual AR therapy and 101 patients on high-dose AR therapy. Nine patients (4.0%) developed bone metastases and transitioned to high-dose AR therapy after a mean interval of 237 days; o these 55.5% subsequently switched from bisphosphonates to denosumab. MRONJ prevalence was 5.5%, limited to the high-dose group (p < 0.001). Tooth extractions (31.0%, p < 0.001), localization to the mandible (83.0%, p = 0.039) and number of AR doses (p = 0,04) were significantly associated with the development of MRONJ. Notably, spontaneous MRONJ accounted for 42.0% of cases. There was no difference in DMFT (Decayed, Missing, and Filled Teeth) scores between patients with and without MRONJ.Conclusions This study demonstrates a significant association between high-dose AR therapy and the development of MRONJ in breast cancer patients, with tooth extractions, mandibular localisation, and cumulative AR exposure identified as risk factors. MRONJ was not observed in the biannual AR therapy group. These findings underscore the importance of comprehensive dental assessments and early risk stratification.