Multicenter retrospective study of incidence of medication-related osteonecrosis of the jaw in breast cancer patients receiving antiresorptive therapy

Medication-related osteonecrosis of the jaw (MRONJ) is one of the most important toxicities of antiresorptive therapy, which is standard practice for patients with breast cancer and bone metastases. The population-based incidence of MRONJ is not well established. A retrospective study at nine breast cancer centers in the Austrian federal state Tyrol found that among patients with breast cancer bone metastases receiving antiresorptive therapy, the incidence MRONJ was 8.8% (95% CI 6.6-11.0): 11.6% (8.0-15.3) among patients receiving denosumab only, 2.8% (0.7-4.8) among patiens receiving bisphosphonates only, and 16.3% (8.8-23.9) among patients receiving bisphosphonates followed by denosumab. The median time to MRONJ after treatment initiation in these three groups was 4.6 years, 5.1 years, and 8.4 years, respectively. The authors conclude that in this population-based study,MRONJ incidence among breast cancer patients with bone metastases was found to be considerably higher, especially for patients receiving denosumab, when compared with available data in the literature. Additionally, patients treated with denosumab only developed MRONJ earlier than what was previously published.