Endocrine Abstracts

Introduction: Immune checkpoint inhibitors (ICIs) are a type of immunotherapy approved for the treatment of certain tumors. As the use of ICIs increases, the incidence of rare side effects, called immune-related adverse effects (IRAE), is also increasing, and can affect different systems (gastrointestinal, hepatic, and endocrine among others), with hyponatremia being a possible side effect in patients treated with ICIs. Our objective is to describe one of the few clinical cases published in the scientific literature that induce SIADH, secondary to pituititis, in patients with monotherapeutic treatment with Nivolumab.

Case report: A 69-year-old man diagnosed with stage IV melanoma, undergoing chemotherapy treatment with Nivolumab, was referred to the Emergency Department from outpatient Medical Oncology clinics due to severe hyponatremia of 103 mmol/l in a follow-up test (prior to the chemotherapy cycle). The patient presents a history of several days of evolution of fatigue, anorexia and hypotension (107/64mmHg; 120 bpm). No fever.

Discussion and conclusions: The possible etiology of hyponatremia would be SIADH in an oncological patient undergoing immunotherapy treatment with Nivolumab. This involvement would be considered secondary to ICI-induced hypophysitis (IRAE), a well-known complication of Lipilimumab, having ruled out adrenal insufficiency and hypothyroidism leading to euvolemic hyponatremia. Nivolumab is a monoclonal antibody that binds to the PD-1 receptor and blocks interaction with its ligands (PD-L1 and PD-L2) located on a large number of cancer cells, quickly establishing itself as the standard of care for locally advanced or metastatic melanoma. It is a very attractive treatment because it achieves better response rates and long-term survival, but due to the growing number of indications, the set of toxicities, in clinical practice, is increasing dramatically. These drugs have been shown to cause a unique set of toxicities that most clinicians were unaware. Therefore, due to their relative novelty and rarity, it is of vital importance that clinicians in the different medical services (Medical Oncology, Emergency Department, Intensive Care United, Primary Care, among others) receive training on the recognition and treatment of potential complications. The use of these drugs in the treatment of a wide variety of malignancies is being investigated, and as their use spreads, it is inevitable that the number of patients with endocrine side effects, such as neurohypophysitis, will increase.