[A Case of Isolated ACTH Deficiency after Conversion Surgery Following Gemcitabine, Cisplatin, and Pembrolizumab for...

We report the case of a 69-year-old man who was initially diagnosed with resectable distal cholangiocarcinoma, for which radical resection was planned. However, the disease was reclassified as an unresectable distal cholangiocarcinoma because peritoneal cytology was positive. After 8 courses of gemcitabine, cisplatin, and pembrolizumab (GCP) therapy, pancreaticoduodenectomy was performed as a conversion surgery because the peritoneal cytology was negative. During surgery, no non-curative factors were identified, and an R0 resection was achieved. On postoperative day 14, the patient developed a fever suspected of cholangitis, and the hyponatremia that appeared on day 20 became prolonged. Suspecting adrenal insufficiency, hydrocortisone replacement was initiated on day 27. The serum sodium levels gradually increased, which allowed tapering of the hydrocortisone dose. As only ACTH levels decreased among the anterior pituitary hormones examined, a diagnosis of isolated ACTH deficiency was made. Ten months postoperatively, the patient received S-1 as adjuvant chemotherapy, continued oral hydrocortisone, and is doing well without adverse events. Clinicians should be aware of irAEs during the perioperative period after ICI therapy. Serious complications can be prevented through multidisciplinary collaboration.