Hypopharyngeal cancer patient with autoimmune myositis and myasthenia gravis emerged after nivolumab administration

Abstract

Abstract Background The immune checkpoint inhibitor(ICI) was approved for head and neck cancer refractory to cDDP, thereafter promptly its survival benefit had been demonstrated. Synergistic effect by combination of SBRT regarded as in situ vaccination and immunotherapy is theoretically expected, but simultaneously an increase in the incidence of irAE by ICI is also concerned. Case A 78-year-old man with T4aN2bM0 hypopharyngeal squamous cell carcinoma of posterior wall type underwent SBRT, which resulted in CR. Afterwards bilateral cervical lymph node metastasis and lung metastasis appeared (rT0N2cM1) and were hit by SBRT, but the right upper deep cervical lesion gradually increased. Then chemotherapy (TXT/CDGP) was performed, which resulted in reduction of pulmonary (MR), but right cervical metastasis was SD, then nivolumab was started. After third course, general fatigue and dysphagia associated with a rise in CK/CKMB appeared. Autoimmune myositis as irAE was suspected and the patient was hospitalized. Mild right ptosis was also observed which was considered at first as Horner symptom since AchR antibody was negative, but tensilon test proved positive, which lead to the diagnosis of autoimmune myositis associated with myasthenia gravis. PSL 1 mg / kg was administrated and gradually decreased every week, then the CK/CKMB value improved remarkably and clinical symptoms were also relieved. The right upper deep neck lesion shrank remarkably on the onset of irAE, but pulmonary metastasis was SD. CR of the neck lesion has persisted to date but the right middle lung field metastatic lesion tended to grow and was submitted to SBRT. Discussion The onset of autoimmune myositis and myasthenia gravis has the risk of leading to fatal heart failure, thus it is mandatory to immediately discontinue treatment and to cope with, regardless of the anti-tumor effect. Regular CK measurement and careful observation are essential on nivolumab administration.