Pembrolizumab as a novel therapeutic option for patients with refractory thymic epithelial tumor: A case report

BACKGROUND Thymic epithelial carcinomas are rare and have a poor prognosis. Treatment of thymic epithelial carcinoma is multimodal and includes surgery, post-operative radiation therapy, adjuvant and neoadjuvant chemotherapy, or exclusive chemotherapy based on disease resectability. However, there is currently no standard treatment regimen for metastatic and recurrent thymic carcinoma. CASE SUMMARY A 45-year-old Caucasian male, with no past medical history, presented with hepatalgia and a cervical mass. A computed tomography (CT) scan showed multiple suspect lesions in the lungs, liver, and anterior mediastinum associated with mediastinal and cervical adenopathy. CT-guided percutaneous biopsies of the liver lesions and anterior mediastinal mass were performed, confirming the histopathology of thymic epithelial carcinoma. Management consisted of several chemotherapy regimens and radiation therapy, administered between April 2016 and December 2018. The patient achieved complete metabolic response. Fluorodeoxyglucose positron emission tomography/CT performed in June 2019 showed disease relapse, with reappearance of a large hypermetabolic hepatic mass and involvement of mediastinal and axillary lymph nodes. Intravenous pembrolizumab (200 mg, every 3 wk) was administered after two prior systemic therapies. The patient’s response to treatment was last documented on March 5, 2020. CONCLUSION Pembrolizumab was successful in treatment of a patient with programmed death-ligand 1-negative metastatic thymic carcinoma, pretreated with chemotherapy.