Nonfunctioning Pituitary Microadenomas: Should Imaging Interval be Extended? A Large Single-center Cohort Study

Context Characterization of the clinical features and natural history of nonfunctioning pituitary microadenomas (NFPmAs) is limited by heterogeneous and small-scale studies. Objective To characterize the clinical presentation and natural history of NFPmAs and evaluate if imaging follow-up interval can be extended. Methods Retrospective single-center cohort study (years 2006-2021) of conservatively managed patients with NFPmAs. Initial symptoms, pituitary function, and tumor size were assessed. A change in NFPmA size >= 2 mm, as determined by pituitary or brain magnetic resonance imaging (MRI), was considered significant. Results There were 347 patients in the study cohort. Headache (78.4%) and fatigue (70.0%) were commonly reported despite no evidence of mass effect or significant pituitary hypofunction. Pituitary deficiencies at baseline were rare, with hypogonadism being most common (5.1%). During a median imaging follow-up period of 29 months (range 3-154), 8.1% of NFPmAs grew. Growth incidence was 2.1 per 100 person-years with a mean and median time to growth of 38.1 (SD +/- 36.4) and 24.5 (interquartile range 12.0-70.8) months, respectively. Tumor growth was mild and not associated with new pituitary deficiencies or visual deficits. Conclusion These data indicate that the natural history of NFPmAs is overall benign. Consequently, we propose that the initial MRI follow-up timeline for NFPmAs can be extended up to 3 years unless a lesion is close to the optic chiasm, there are worrisome mass effect symptoms, or new pituitary deficiencies.