Bisphosphonate-induced osteonecrosis of the jaw: Incidence and risk factors in patients with breast cancer and gynecological malignancies

Abstract

1113 Background: Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption. They are successfully used in conditions of increased bone turnover such as osteoporosis or bone metastases. Since 2003 multiple cases of bisphosphonate-induced osteonecrosis of the jaw (ONJ) were reported. Our purpose was to describe the incidence and risk factors of ONJ in patients with breast cancer or gynecological malignancies. Patients and Methods: ONJ was assessed retrospectively for all patients with breast cancer or gynecological malignancies treated with bisphosphonates at the Department of Gynecology and Obstetrics, University Hospital Tuebingen during April 1999 until May 2006. Results: 10 of 310 (3%) patients with breast cancer or gynecological malignancies developed ONJ while receiving bisphosphonate therapy. All patients with ONJ were treated for bone metastases. Except one all patients with ONJ had a history of recent dental procedures. All patients had received zoledronic acid as part of their bisphosphonate regimen. In 4 of 10 patients this was the only bisphosphonate given. The remaining 6 patients had received at least one of the other bisphosphonates (alendronate, ibandronate, clodronate or pamidronate) before or after zoledronic acid therapy during their course of disease. Time of exposure to bisphosphonates and the number of treatment cycles were significant risk factors for the development of ONJ (p<0.001). In patients diagnosed with ONJ the mean number of treatment cycles was 27 ±18 cycles (median: 21 cycles, range 6–62 cycles) and the mean duration of bisphosphonate therapy was 29 ±20 months (median: 22 months, range 1–67 months). In contrast, the mean number of treatment cycles in patients without manifestation of ONJ was 11 ±12 cycles (median: 6 cycles, range 1–90 cycles). The mean duration of therapy was 12 months (median: 7 months, range 1–81 months). Conclusion: Osteonecrosis of the jaw is regarded a major side effect of bisphosphonate therapy. Length of exposure to bisphosphonates and the number of treatment cycles seem to be the most important risk factors for the development of ONJ. In addition, recent dental procedures favours the development of an ONJ. No significant financial relationships to disclose.