CNSC-77. IMMUNE CHECKPOINT INHIBITORS IN THE TREATMENT OF AGGRESSIVE PITUITARY ADENOMAS AND CARCINOMAS

Abstract While pituitary tumors are generally benign lesions, aggressive pituitary tumors (APTs) and pituitary carcinomas (PCs) are found in less than 1% of cases. Though temozolomide has traditionally been used postoperatively as a first-line agent, 30-50% of patients continue to show progressive disease. Immunotherapy has shown promise over the past decade in the treatment of these highly-resistant pituitary tumors; however, large-scale studies are limited. Our study conducted a systematic review of all Pubmed articles related to cases of aggressive pituitary adenomas and carcinomas treated with immunotherapy. Demographic, treatment, and outcome data from 12 studies were extracted for further analysis. Of the 29 included patients, 13 patients were found to have locally-invasive APTs and 16 patients were diagnosed with PCs. The combination of ipilimumab and nivolumab was most commonly reported immunotherapeutic agent (72.4%) and the other patients received either pembrolizumab (24.1%) or an unidentified anti-PD-1 agent (3.4%). In APT patients, 7.7% showed a complete response, 7.7% showed partial response, 38.5% showed stable disease, and 46.2% showed disease progression. In PC patients, 43.8% patients showed a partial response, 12.5% showed stable disease, and 43.8% patients showed disease progression. Of the 20 patients for whom Ki-67 indices were reported, 4/8 (50%) patients with Ki-67 ≥30% showed complete (1/8) and partial (3/8) responses, 2/8 (25%) patients showed stable disease, and 2/8 (25%) showed progressive disease. In contrast, 2/12 (16.7%) patients with Ki-67 <30% showed partial response, 2/12 (16.7%) patients showed stable disease, and 8/12 (66.7%) patients showed progressive disease. In patients with aggressive pituitary adenomas and carcinomas, tumors with Ki-67 ≥30% demonstrate an improved response to immunotherapy compared to tumors with Ki-67 <30%, with complete or partial responses seen in 50% of our sampled patients. Our findings suggest postoperative management of aggressive pituitary tumors should be guided by immunohistologic biomarkers.