Osteonecrosis of the jaw (ONJ) in patients with prostate (PC) or breast (BC) cancer treated with bisphosphonates: Study of the effect of the application of preventive measures

16025 Background: Bisphosphonates are used in the treatment of bone metastases but their use is associated with the development of ONJ. Dental problems or interventions are precipitating factors of ONJ. Since 2003, we have implemented assessment (and management) of dental problems of all patients who are candidates for or who are on treatment with bisphosphonates by specialists with experience on ONJ. We also recommend improved oral hygiene and we avoid dental procedures during treatment. We have recently shown that these preventive measures have resulted in reduction of the incidence of ONJ caused by Zoledronic acid in MM. We have investigated whether ONJ also decreased after the implementation of these measures in two solid tumors with high frequency of bone metastases: prostate and breast cancer. Methods: Patients should have had at least six months of treatment with Pamidronate, Zoledronic acid, or successive use of Pamidronate and Zoledronic acid. Patients were classified into two groups depending on the date of initiation of treatment: before (Group A) or after (Group B) the implementation of the preventive measures (January 2003). The proportions of patients with osteonecrosis between the two groups were compared with the Fisher's exact test. Times of exposure were compared using the Mann-Whitney-test. Results: Seventy-seven patients with PC (Group A: 25, Group B: 52) and 109 with BC (Group A: 57, Group B: 52) were included in the analysis. The first bisphosphonate treatment in PC patients was administered on 10/9/1997 and in BC patients on 15/11/1996. Among PC patients, there were 3 cases of ONJ (3.9%) after a median time of exposure of 15 months. All ONJ cases belonged to Group A (12%, p=0.011 for comparison with Group B). The median time of exposure between the two groups was similar (16 months vs. 14 months, p=0.698). There were 2 cases of ONJ among BC patients (1.8%) after a median time of exposure of 18 months. One case was observed in Group A and the other in Group B (p=0.948). Exposure was similar between the two groups (19 vs. 17 months, p=0.335). Conclusions: The implementation of preventive measures seems to reduce the occurrence of ONJ in PC patients. In BC, ONJ is rare and no impact of these measures was found. No significant financial relationships to disclose.