Pituitary Enlargement and Hypopituitarism in Patients Treated with Immune Checkpoint Inhibitors: Two Sides of the Same Coin?

Background: Immune checkpoint inhibitor hypophysitis (IIHs) is an emerging problem in cancer patients treated with immune checkpoint inhibitors (ICIs). We aimed to describe the clinical and molecular features of a multicenter series of IIHs. Methods: Demographic and clinical features were retrospectively collected for all cases. Anti-pituitary and anti-hypothalamus autoantibodies were also measured. Results: Nine patients were included. Six patients were treated with nivolumab and three with ipilimumab. Secondary hypoadrenalism was diagnosed in all patients. Pituitary MRI showed pituitary enlargement in two cases and no abnormalities in the other seven. Anti-pituitary antibodies were positive in 57.1% of cases and anti-hypothalamus antibodies in 85.7% of cases. Multidisciplinary treatments were established by a neuroendocrinologist and oncologists: all patients were treated with hydrocortisone replacement; ICI was withdrawn in two cases. At follow-up, hypoadrenalism persisted in all cases. Pituitary enlargement on MRI spontaneously recovered in the two affected patients. We found that the typical features of hypophysitis involved more frequently females and patients treated with ipilimumab. Conclusions: Although this study did not clarify if autoimmune secondary hypoadrenalism and ICI hypophysitis on brain imaging are two sides of the same disease, our preliminary data underline the need for molecular studies of IIHs and of autoimmune ICIs-related hypopituitarism.