Incidence of antiresorptive agent-related osteonecrosis of the jaw: A multicenter retrospective epidemiological study in Hyogo Prefecture, Japan.

Background/purpose: The incidence of medication-related osteonecrosis of the jaw is increasing worldwide, mostly due to the use of antiresorptive agents (ARAs) such as bisphosphonate (BP) and denosumab (Dmab). However, the proportion of BP-related osteonecrosis of the jaw (BRONJ) and Dmab-related osteonecrosis of the jaw (DRONJ) among all ARA-related osteonecrosis of the jaw (ARONJ) cases is not clear; this hinders appropriate treatment, recurrence-prevention planning, and avoidance of unnecessary Dmab withdrawal. Moreover, the causative drug administered at each disease stage remains unknown. Therefore, we conducted a retrospective study of patients with ARONJ who visited oral and maxillofacial surgery departments at hospitals in Hyogo Prefecture, Japan, over 3 years to classify and compare patient characteristics with those having BRONJ and DRONJ. We sought to identify the proportion of DRONJ in ARONJ. Materials and methods: After excluding stage 0 patients, 1021 patients were included (471 high-dose; 560 low-dose). ARA treatment for bone metastases of malignant tumors and multiple myeloma was considered high dose, while that for cancer treatment-induced bone loss and osteoporosis was low dose. Results: Low doses of BP and Dmab accounted for >50% patients; the results differed from those in other countries. DRONJ accounted for 58% and 35% of high-dose and low-dose cases, respectively. Stage 3 ARONJ cases comprised 92 (19.5%) low-dose BRONJ, 39 (20.1%) high-dose BRONJ, 24 (30%) low-dose DRONJ, and 68 (24.5%) high-dose DRONJ. Eighty-nine patients who received switch therapy were divided into BRONJ or DRONJ, but there was no difference in the ratio of each stage compared to the non-switch therapy. Conclusion: To the best of our knowledge, this is the first study to clarify the proportion of BRONJ and DRONJ cases, causative drug, and its doses by disease stages. DRONJ accounted for approximately 30% of the ARONJ, approximately 60% of which was due to high doses.