Metastatic HER2-positive breast cancer complicated by medication-related osteonecrosis of the jaw

What happened, in summary

This 64-year-old woman had a history of Parkinson disease and HER2-positive breast adenocarcinoma. The breast cancer was first diagnosed in 2009 and treated with surgery, local radiotherapy, and ongoing chemotherapy. In 2019, she developed recurrence with osseous metastasis and received chemotherapy plus antiresorptive therapy to protect the bones. That bone-directed treatment included one intravenous dose of alendronate/Zometa 4 mg followed by 5 intravenous administrations of denosumab/Xgeva, with a cumulative denosumab dose of 600 mg. She later developed severe dental pain involving the lower left teeth while continuing chemotherapy, including doxorubicin/Myocet, cyclophosphamide/Endoxan, and paclitaxel/Taxol. The pain initially resembled dental disease, and she underwent several dental evaluations, scaling, endodontic workup, radiographs, and cone-beam CT. Extraction of the lower left second premolar was performed with amoxicillin prophylaxis so the clinicians could explore the bone. Necrotic bone was found in the socket, supporting medication-related osteonecrosis of the jaw, or MRONJ, rather than a simple dental infection. Follow-up was delayed by the first COVID-19 wave. Five months after the first oral surgery, another extraction and osteotomy were performed for the lower left first premolar. The lower left canine was kept because it remained vital and removing it could have caused more bone trauma. Her story is best understood as metastatic HER2-positive breast cancer complicated by antiresorptive-associated jaw osteonecrosis that required oral-surgery management while cancer treatment continued. The dental findings progressed across several teeth, showing how MRONJ can masquerade as routine endodontic or periodontal disease before necrotic bone is directly seen.