Diabetes mellitus induced by immune checkpoint inhibitors: type 1 diabetes variant or new clinical entity? Review of the literature

Immune Check-Point Inhibitors (CPIs) have improved long-term patients' outcomes in several advanced cancers. Diabetes mellitus induced by CPIs (CPI-DM) is considered the second most frequent endocrine CPIs' side effects with a variable prevalence up to 2%. The aim of our study was to identify CPI-DM characteristics and differences from the classical form of diabetes. Therefore, we conducted a structured Pubmed® search collecting publications dated from January 2015 to December 2019. A total of 642 citations were identified and 121 publications met our study criteria. We analyzed 200 case reports, including our 3 cases under publication. The majority of CPI-DM occurred with anti-Programmed cell Death-1 in monotherapy or in combination, although few cases with Programmed cell Death Ligand-1 and Cytotoxic T Lymphocyte Antigen 4 were reported. Generally, CPI-DM arose early (an average of 9 weeks after CPIs starting), but also after the end of CPIs treatment. In all patients, CPI-DM has an acute onset and in 67.5% of cases diabetic ketoacidosis occurs. C-peptide levels were usually and permanently compromised, requiring lifelong insulin therapy. Moreover, autoimmunity and genetic profile was not always helpful. In particular, anti-glutamic acid decarboxylase (anti-GAD) antibodies and Human Leukocyte Antigen (HLA) DR4 were present in only 43.0% and 51.3% of cases respectively. In 51.0% of subjects a mild exocrine impairment coexisted. In short, though CPI-DM has similarities to type 1 diabetes mellitus, it represents a new, largely unknown, clinical entity. In addition, as CPI-DM is a relative frequent side-effect under CPI, a close monitoring of the glucose levels and early signs and symptoms of diabetes in patients affected by neoplasm is recommended.