The natural history of non-functioning pituitary adenomas: A meta-analysis of conservatively managed tumors

Background: Non-functioning pituitary adenomas (NFPA) are often discovered incidentally. The natural history of NFPA is not well understood, obfuscating evidence-based management decisions. Meta-data of radiographically followed NFPA may help guide conservative versus operative treatment of these tumors. Methods: We searched PubMed, Medline, Embase, and Ovid for studies with NFPA managed nonopera-tively with radiographic follow-up. Studies on postoperative outcomes after NFPA resection and studies that did not delineate NFPA data from functional pituitary lesions were excluded. NFPA were divided into micro-and macroadenomas based on size at presentation. We performed a meta-analysis of aggregate data for length of follow-up, change in tumor size, rate of apoplexy, and need for resection during follow-up. Results: Our database search yielded 1787 articles, of which 19 were included for final analysis. The stud-ies included 1057 patients with NFPA followed radiographically. Macroadenomas were significantly more likely to undergo growth (34% vs. 12%; p < 0.01) or apoplexy (5% vs. < 1%; p = 0.01) compared to microadenomas. Resection was performed in 11% of all NFPA patients during follow-up regardless of size at presentation. Meta-regression showed that surgery during follow-up was associated with macroade-nomas and negatively associated with microadenomas that decreased in size. Conclusion: Low-quality evidence suggests that NFPA classified as macroadenomas have an increased rate of growth and apoplexy during follow-up compared to microadenomas. A significant minority of all NFPA patients ultimately underwent surgery. In select patients, nonoperative management may be the appropriate strategy for NFPA. Macroadenomas may require closer follow-up. (c) 2021 Elsevier Ltd. All rights reserved.