Natural history of nonfunctioning pituitary microadenomas: a systematic review and individual participant data meta-analysis

Abstract Objective Increased frequency of neuroimaging has led to enhanced identification of small nonfunctioning pituitary adenomas (NFPAs) leading, in many cases, to extensive follow-up. However, the value of ongoing monitoring of these incidental lesions remains unclear. The study aims to determine the need for surgical intervention and assess the risks of developing new endocrinopathies during follow-up in patients with conservatively treated micro-NFPAs. Design A systematic review and individual participant data (IPD) meta-analysis. Methods We conducted a bibliographical search of PubMed and EMBASE to identify relevant studies. Authors of eligible studies were invited to share IPD. Cohort studies including patients with conservatively treated micro-NFPAs with at least 1 follow-up magnetic resonance imaging were considered eligible. Fourteen studies met inclusion criteria. Six authors provided IPD (N = 647). Data were reanalyzed for verification. In cases of discrepancies the original authors were contacted for authentication. Results Risk estimates were reported as number of events per 100 person-years (PYs). Estimates were pooled using the 2-step approach. Overall probability of surgery was 0.2/100 PYs (95% CI: 0.0-0.4; I2 = 28%). Probability of surgery due to visual impairment was 0.1/100 PYs (95% CI: 0.0-0.2; I2 = 0%). Both were independent of baseline tumor size (≥6 or <6 mm), sex, or age (P values >.40). Risk of developing a new endocrinopathy was 1.0/100 PYs (95% CI: 0.4-1.6; I2 = 0%). Data for classical meta-analysis were available for 7 studies (N = 1089) and supported the IPD results. Conclusions These data suggest that routine follow-up of micro-NFPAs can be reduced significantly and that available guidelines should be revisited.