Magnetic resonance imaging features of hypophysitis in patients with cancer treated with immune checkpoint inhibitors.

Immune checkpoint inhibitors (ICIs) have significantly improved outcomes in several solid malignancies but are associated with endocrine immune-related adverse events (irAEs), particularly hypophysitis. This retrospective real-world data study aimed to assess the magnetic resonance imaging (MRI) findings in cases with immune-related (ir) hypophysitis. Sixty-six cancer patients treated with ICIs at Laikon General Hospital between January 2016 and September 2024, presenting with anterior pituitary hormone deficiencies, were included. All patients underwent baseline pituitary MRI at the time of ir-hypophysitis diagnosis (median time: 2 weeks post-diagnosis). A follow-up MRI was also available in 37 patients (median time: 1.6 years post-diagnosis). All scans were centrally reviewed by radiologists blinded to clinical data. Baseline MRI abnormalities demonstrated pituitary enlargement (25%), reduced enhancement (10%), empty sella (8.3%), heterogeneous enhancement (5%), reduced size (3.3%), and stalk deviation (1.7%). Among 31 patients with both baseline and follow-up MRIs, 45% showed imaging changes (partially empty sella, size alterations). No specific ICI regimen was associated with characteristic imaging patterns. Patients with multiple hormonal axis deficiencies had more frequent MRI abnormalities than those with isolated ACTH deficiency (68.4% vs. 46.3% initially; 71.3% vs. 56.4% at follow-up). Pituitary MRI abnormalities are present in approximately half of patients with ir-hypophysitis, with dynamic changes observed in follow-up imaging. However, the absence of findings in a substantial proportion highlights the limited sensitivity of MRI in this irAE and underscores the importance of clinical and biochemical evaluation.