Onset of MRONJ in Breast Cancer Patients after Switching from Low to High Dose of Bone Modifying Agents Due to Bone Metastases Development: A Single Center Retrospective Cohort Study

Background: Medication-Related Osteonecrosis of the Jaw (MRONJ) is an adverse drug reaction mainly associated to bone modifying agents (BMAs). Breast cancer (BC) is the most frequent cancer worldwide. Its therapy can cause cancer treatment-induced bone loss (CTIBL), commonly treated with BMAs. The aims of this retrospective study are: to describe characteristics of BC patients under BMAs for CTIBL; to record any switch to high-dose BMAs; to assess MRONJ onset and to identify any factors associated with it. Patients: Authors included patients referred for MRONJ prevention to the Unit of Oral Medicine (University Hospital of Palermo). Results: Fourteen female BC patients under low-dose BMAs for CTIBL were eligible (mean age 66.6 years). Four patients switched to high-dose BMAs for bone metastases. In two of the four, MRONJ developed: one case, in the mandible (risedronate for 48 months then Xgeva® for 60 months); the other case, in the maxilla (Prolia® for 20 months then zoledronate for 16 months). Conclusion: It can be theorized that BC patients under BMAs for CTIBL are likely to have MRONJ risk similar to osteo-metabolic patients. These patients need more careful monitoring of oral health since they may switch, for preventing or treating bone metastases, to heavier BMAs therapy, thus increasing their risk of MRONJ.