Managing severe dermatitis and grade 4 pneumonitis in a patient with non-small-cell lung cancer following pembrolizumab treatment: A case report.

Inhibitors of the programmed death receptor 1 (PD-1) or its ligand PD-L1 are widely used in cancer treatment. Despite their efficacy, these immunotherapies can induce adverse effects, particularly dermatitis and pneumonitis. However, the prognosis of these conditions is infrequently reported. The present study discusses a case of a patient with non-small-cell lung cancer (NSCLC) who developed severe dermatitis and grade 4 pneumonitis following treatment with pembrolizumab. Initially, the patient was administered methylprednisolone at a dosage of 4 mg/kg/day. Reducing the dosage to 1 mg/kg/day exacerbated the pneumonitis, following which the patient was administered mycophenolate mofetil (MMF), which notably ameliorated both conditions. The methylprednisolone dosage was then gradually reduced to 4 mg daily. The present case represents a rare instance of simultaneous severe dermatitis and grade 4 pneumonitis in a patient with NSCLC following immunotherapy. The conditions were successfully managed with a combination of MMF with methylprednisolone, resolving the steroid-dependent dermatitis and pneumonitis. The patient maintained a partial remission, with a tumor size of >30% smaller compared with the initial tumor size, for >3 years following the cessation of immunotherapy.