Predictive capacity of mismatch repair status in the use of immune checkpoint inhibitors for the treatment of aggressive pituitary tumors and pituitary carcinomas: An illustrative case report and literature review

Background: Aggressive pituitary tumors (APTs) 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 pooled case analysis of all PubMed and Scopus articles related to cases of APTs and PCs treated with ICIs. Data from 12 studies were extracted for further analysis, including a single case from our institution of an APT patient who achieved a complete response (CR) with ICI therapy which was presented as an illustrative report. Results: Of the 29 included patients, 13 patients were found to have APTs and 16 patients were diagnosed with PCs. The overall response rate 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 CR or partial response (PR), while 0/8 patients with intact MMR function showed complete or partial treatment responses ( P = 0.006). Conclusion: MMR mutation in APT and PC patients was associated with a statistically significant higher likelihood of attaining a CR or PR to ICI therapy. While current recommended first-line therapy involves the administration of TMZ following initial radiotherapy or surgical resection, future studies should assess whether certain patient subpopulations (e.g., based on MMR mutational status) may show superior clinical results with ICI therapy.