Hepatotoxicity and Recurrent NSTEMI While on Pembrolizumab for Metastatic Giant Cell Bone Tumor.

We present the first reported case showing metastatic giant bone cell tumor being treated successfully with pembrolizumab after failing prior tyrosine kinase inhibitor therapy. Of note, the patient developed multiple systemic effects associated with checkpoint inhibitor use. One year after starting the checkpoint inhibitor (ICI), the patient also developed hepatitis that was confirmed by liver biopsy and pathology to be, in part, due to drug-mediated toxicity similar to prior ICI toxicity cases that have been reported. Additionally, although the patient had vascular risk factors (hypertension, diabetes and smoking), it was notable from a cardiology perspective that the patient developed 2 subsequent non-ST-elevation myocardial infarctions, with rapid progression of stenosis of the left circumflex artery 2 months apart. The first left heart catheterization showing minimal disease of the left circumflex, but 2 months later, presenting with chest pain, a repeat left heart catheterization showed significant stenosis of the left proximal circumflex, raising the possibilities that either ICI can promote plaque rupture and/or accelerated atherosclerosis; both phenomena have been shown to occur in animal models. The patient also developed thyroiditis with subsequent hypothyroidism, now on thyroid replacement from checkpoint inhibitor use. This case demonstrates the multiorgan adverse effects this new antioncologic agent can have and yet also its promising antitumor effects. Awareness of the side effects among primary care doctors and all specialists will be helpful in managing these potential side effects and research will help elucidate ways to prevent the adverse effects.