Immunotherapy-Associated Hypophysitis under Anti-PD1: Two Case Reports

Background: Immunotherapy-associated hypophysitis is an uncommon adverse event. However, if not handled properly, it could lead to fatal sequelae. Case Presentations: Case 1. A 66-year-old man presented to our hospital with hyponatremia. He had low plasma levels of adrenocorticotropin and cortisol. The patient had a history of non-small cell lung cancer and had undergone 16 cycles of immunotherapy with sintilimab, a monoclonal antibody against programmed cell death protein 1 (PD1). He was diagnosed with adrenal insufficiency secondary to immunotherapy-associated hypophysitis and received a physiological dose of glucocorticoids. Upon discharge, he has prescribed a continued course of hormone replacement therapy combined with immunotherapy. Case 2. The second case profiled here involved a 58- year-old patient diagnosed with gastric antrum cancer. After ten months of immunotherapy with carrelizumab, a human high-affinity immunoglobulin G4 (IgG4) anti-PD-1 monoclonal antibody drug, the patient was referred to the Endocrinology Department at our medical centre for adrenal nodules and intolerance of anorexia. He also suffered from hypophysitis and was prescribed hormone replacement therapy combined with immunotherapy. Conclusion: This article discusses the clinical characteristics, diagnosis, treatment, and subsequent follow-up for immunotherapy-associated hypophysitis in the context of two case reports. Based on our findings and observations, we conclude that patients with immunotherapy should regularly be referred to endocrine-related follow-up during tumour treatment.