Predictive Capacity of Mismatch Repair Status in the Use of Immune Checkpoint Inhibitors for the Treatment of Aggressive Pituitary Adenomas and Pituitary Carcinomas: Illustrative Case Report and Literature Review

Introduction Aggressive pituitary adenomas (APAs) and pituitary carcinomas (PCs) are rare tumors that often recur despite surgery and radiation. Immune checkpoint inhibitors (ICI) present a promising treatment alternative for these tumors; however, there is a paucity of information in the literature correlating specific tumor genomics with clinical responses. Methods Our study conducted a systematic review of all Pubmed and Scopus articles related to cases of APAs and PCs treated with ICIs. Data from 12 studies were extracted for further analysis, including a single case from our institution of an APA patient who achieved a complete response with ICI therapy which was presented as an illustrative report. Results Of the 29 included patients, 13 patients were found to have APAs and 16 patients were diagnosed with PCs. The overall response rate (ORR) for our study population was 24.1%. Of the 14 patients for whom mismatch repair (MMR) data were reported, 4/6 (66.7%) of patients with MMR mutation showed a complete or partial response, while 0/8 patients with intact MMR function showed complete or partial treatment responses (p = 0.006). Conclusion MMR mutation in APA and PC patients was associated with a statistically significant higher likelihood of attaining a complete or partial response to ICI therapy. While current recommended first-line therapy involves the administration of TMZ, future studies should assess whether certain patient subpopulations (e.g., based on MMR mutational status) may show superior clinical results with ICI therapy.