FRI331 Autoimmune Hypophysitis Secondary To Ipilimumab And Nivolumab Combination Therapy In A Patient With Advanced Renal Cell Carcinoma

Disclosure: E.Y. Ibrahim: None. I. Hulinsky: None. D. Regelmann: None. Introduction: Ipilimumab and nivolumab combination therapy is an effective immune checkpoint inhibitor regimen indicated for advanced stages of renal cell carcinoma. Autoimmune hypophysitis is a rare adverse event from this therapy that occurs in only 3-6% of patients. The mechanism underlying immune checkpoint inhibitor-induced hypophysitis is not fully understood but involves immune, inflammatory, and genetic factors. Clinical Case: A 65-year-old male with a history of hypertension and type 2 diabetes mellitus, recently diagnosed with renal cell carcinoma with metastasis to the lungs presents to the emergency department with three days of generalized weakness and worsening confusion, accompanied by 2 weeks of headache. Two months prior to presentation, the patient began chemotherapy with four cycles of nivolumab and ipilimumab. The emergency department team initiated a stroke code for right facial droop and right-sided weakness seen on his physical exam. The CT of the patient’s head was unremarkable. The patient was also hypotensive (BP 90/40 mmHg) and tachycardic (140 bpm). He received 3 liters of crystalloid as well as diltiazem injection without improvement. Random cortisol on admission at 11:00 am was 1 ug/dl (3.4-22), ACTH was 7 pg/mL (6-50), Na was 135 mEq/L (137 - 145) and K was 5.1 mEq/L (3.5 - 5.0). Furthermore, TSH 0.02 μIU/ml (0.47-4.70), ILGF 39 ng/mL (41-279), and total testosterone levels <3 ng/dL (139-740) were low. The free thyroxine level was measured at 1.00 ng/dL (0.8-1.9), and MRI revealed a normal sella tursica. Based on these findings, we diagnosed the patient with hypopituitarism, likely due to hypophysitis as an immune-related adverse event of immune checkpoint inhibitor therapy. Consequently, we discontinued the administration of Ipilimumab-Nivolumab combination therapy and started oral dexamethasone 8 mg and fludrocortisone 0.1 mg for mineralocorticoid supplementation. The patient’s symptoms resolved, and laboratory data showed improvements in hyponatremia, hyperkalemia, and hypoglycemia. The care team transitioned the patient’s steroid regimen to prednisone 25 mg daily maintenance dose, and the patient was discharged with stress dosing instructions. Conclusion: Diagnosis of hypophysitis as an immune-related adverse event is challenging due to its vague presentation. However, a delayed diagnosis can be life-threatening. As a result, clinicians must maintain a high index of suspicion for presentations of weakness and headache in consistent clinical contexts, in order to provide optimal management and minimize morbidity. Additionally, early management of hypophysitis can reduce the interval of immune checkpoint inhibitor therapy, which in turn affects the course of cancer. Presentation: Friday, June 16, 2023