Prevalence of hypophysitis in a cohort of patients with metastatic melanoma and prostate cancer treated with ipilimumab

Ipilimumab is a human monoclonal antibody directed against cytotoxic T-lymphocyte antigen-4, that has been shown to significantly improve survival in patients with metastatic melanoma. Blocking cytotoxic T-lymphocyte antigen-4 elicits T cell activation, proliferation and anti-tumor response, but can also trigger immune-related adverse events. Among immune-related endocrinopathies, hypophysitis represents the most frequent, with an incidence up to 17% in patients treated with ipilimumab. We report nine cases of ipilimumab-induced hypophysitis in a cohort of 273 patients treated with ipilimumab between 2006 and 2015, as part of clinical trials or after its marketing. Thyroid function tests were scheduled at screening and during follow up (every 21 days) in all patients. Cortisol, adrenocorticotropic hormone, follicle-stimulating hormone, luteinizing hormone, and estradiol (for females) or testosterone (for males), prolactin, growth hormone, insulin-like growth factor 1 were measured only in case of clinical suspicion. The incidence of hypophysitis was 3.3%. The most frequent pituitary failure was adrenocorticotropic hormone and thyroid stimulating hormone secretion with a complete recovery of thyroid stimulating hormone, but not of adrenocorticotropic hormone during follow up. All patients had negative pituitary antibodies. The main symptoms at diagnosis were fatigue and headache. Clinicians should be aware about the risk of hypophysitis during treatment with immune check-point inhibitors and the necessity of investigating pituitary function during therapy. Pituitary magnetic resonance imaging does not seem pivotal for a definite diagnosis if not performed at the onset of disease.