Isolated
adrenocorticotropic hormone (
ACTH) deficiency is a rare immune-related adverse event associated with
immunotherapy using
immune checkpoint inhibitors for malignant
tumors. A 68-year-old man had previously undergone a complete
gastrectomy with regional
lymph-node dissection for remnant gastric
cancer, with a final diagnosis of T4aN2M1, Stage IV. Because he developed
lymph-node metastases during postoperative
chemotherapy using S-1 plus
oxaliplatin, he was treated with
ramucirumab plus
nab-paclitaxel. Eight months after the operation, the patient developed multiple liver
metastases and was treated with
nivolumab (3 mg/kg, every 2 weeks). After four cycles of
nivolumab treatment, the
cortisol level decreased, and the patient reported general
fatigue and appetite loss. Pituitary stimulation testing using a combination of
corticotropin-releasing hormone,
luteinizing hormone-releasing hormone, and
thyrotropin-releasing hormone revealed markedly low
ACTH and
cortisol responses. Magnetic resonance imaging revealed no enlargement of the pituitary gland or thickening of the stalk. After
steroid replacement
therapy using
hydrocortisone, the patient's symptoms of general
fatigue improved. After discharge,
nivolumab and
steroid replacement were continued. During the subsequent 6 months, the
clinical course of the patient was mostly uneventful. Abdominal computed tomography revealed a marked shrinkage of liver and
lymph-node metastases, which indicated a partial response with a 95.0% decrease in target lesions compared with baseline. To the best of our knowledge, this is the first case reported in the English literature of a patient who developed
isolated ACTH deficiency during
nivolumab treatment for a metastatic advanced
gastric cancer.