THU018 Remarkable Response Of ACTH-secreting Pituitary Carcinoma To Immune Checkpoint Inhibitors: A Case Report

Disclosure: J. Park: None. W. Choi: None. A. Hong: None. J. Yoon: None. H. Kim: None. H. Kang: None. Background: ACTH-secreting pituitary carcinoma transformed from Cushing’s disease is very rare and has aggressive characteristics with limited treatment options. We report a case of ACTH-secreting pituitary carcinoma patient who showed a excellent response to immune checkpoint inhibitors (ICIs). Clinical Case: A 70-year-old female presented with a rapidly growing pituitary carcinoma transformed from Cushing’s disease after bilateral adrenalectomy. Her tumor initially responded to 6 cycles of temozolomide and 7 cycles of temozolomide plus capecitabine. However, multiple brain and pulmonary metastases were newly seen on following imaging studies and the patient had worsening generalized pigmentation on her whole body with newly developed headache, diplopia, and ptosis of the left eye. After introduction of three cycles of ipilimumab plus nivolumab therapy, her plasma ACTH level decreased dramatically from 58,000 pg/ml to 198 pg/ml with improving skin pigmentation and headache episodes. We maintained nivolumab and observed that the plasma ACTH level be normalized to 44 pg/ml (normal range: 6 – 60 pg/ml). Her follow-up brain MRI and chest CT scan also showed marked response, some of the chest lesions even showed nearly complete response (figure 1). On the last follow-up visit, we confirmed that she was in good general condition and tolerable to nivolumab maintenance therapy with glucocorticoid replacement. Conclusion: Immune checkpoint inhibitors (ICIs) may be effective therapeutic options in aggressive pituitary carcinoma and can be considered in temozolomide resistant cases. Moreover, because of the excessively high cost, we emphasize the necessity of clinical trials of ICIs for rare diseases like pituitary carcinomas to expand insurance coverage and reduce the unmet needs of medical care. References:(1) Reincke, M., et al., Corticotroph tumor progression after bilateral adrenalectomy (Nelson's syndrome): systematic review and expert consensus recommendations. Eur J Endocrinol, 2021. 184(3): p. P1-P16. (2) Raverot, G., et al., Temozolomide treatment in aggressive pituitary tumors and pituitary carcinomas: a French multicenter experience. J Clin Endocrinol Metab, 2010. 95(10): p. 4592-9. (3) Lin, A.L., et al., Marked Response of a Hypermutated ACTH-Secreting Pituitary Carcinoma to Ipilimumab and Nivolumab. The Journal of Clinical Endocrinology & Metabolism, 2018. 103(10): p. 3925-3930. (4) Raverot, G., et al., Aggressive pituitary tumours and pituitary carcinomas. Nat Rev Endocrinol, 2021. 17(11): p. 671-684. Presentation: Thursday, June 15, 2023