Medication-Related Osteonecrosis of the Jaw (MRONJ) induced by a CDK-4/6 inhibitor (Palbociclib) in a patient who was naïve to Antiresorptive Bone Therapy: A Case Report

Medication-related osteonecrosis of the jaw (MRONJ) is a well-documented adverse effect initially linked to antiresorptive agents such as bisphosphonates. Over time, other drug classes have been associated with MRONJ: monoclonal antibodies targeting RANK ligand, monoclonal antibodies targeting VEGF, tyrosine kinase inhibitors, and mammalian target of rapamycin (mTOR) inhibitors. This article presents the case of an 83-year-old female patient referred to the maxillofacial surgery department due to a submental cutaneous fistula with purulent discharge and localized pain. Her notable medical history includes treatment with palbociclib and exemestane for breast cancer. Palbociclib (cyclin-dependent kinase [CDK] 4/6 inhibitors) are commonly used in combination with hormone therapy for the treatment of HR+/HER2- metastatic breast cancer. Whereas its efficacy in prolonging progression-free survival is well established, its potential impact on bone remodeling and the risk of MRONJ remain under investigation. This case highlights a potential new etiology of MRONJ associated with palbociclib. As CDK 4/6 inhibitors gain widespread use in oncology, clinicians should be aware of this possible complication and closely monitor patients for signs of jaw osteonecrosis.