PMON153 Changes in size of pituitary microadenomas, a retrospective cohort study

BACKGROUND: The estimated prevalence of pituitary lesions is 22.5% in radiologic studies. The solid and/or cystic lesions are usually described as incidentaloma. Most pituitary incidentalomas are microadenomas (lesion size <1 cm). In 2011, The Endocrine Society published guideline on following incidental pituitary lesion. However, few studies evaluated the dynamic changes in pituitary incidentaloma. Method: In this retrospective cohort study, patients with pituitary microadenomas were identified from our institution database by the Research Patient Data Registry from 11/2003 to 3/2021. We performed chart review to collect data relevant to demographic and pituitary imaging findings. The study was approved by our institution IRB.The patients with the diagnosis of pituitary microadenoma (tumor size < 10 millimeter (mm)) were included in this study. To eliminate the medication effects on the tumor size, we excluded the patients with diagnosis of prolactinoma and patients on dopamine agonists or somatostatins. We performed linear regression test. We performed Kaplan-Meier survival curve analysis. RESULTS: Over 15 years, among total 177 subjects, 78 (44%) had unchanged size of the microadenoma, 49 (27%) had increase size, 34 (19%) had decrease in size, and 16 (9%) had both increased and decreased size. Ten (6%) subjects had transsphenoidal pituitary tumor resection. Among 128 female subjects, 53 (41%) had unchanged size, 35 (27%) had increased size, 28 (22%) had decreased size, and 12 (9%) had both increased and decreased size. Seven subjects (5%) had transsphenoidal pituitary tumor resection. Among 49 male subjects, 25 (51%) had unchanged size, 14 (27%) had increased size, 6 (12%) had decreased size, and 4 (8%) had both increased and decreased size. Three patients (6%) had tumor resection. Over the 15 years, the changes in the size of microadenomas are between -6 mm to 6 mm. There were 6 (3%) subjects with tumor size increase into macroadenoma category. The slope by linear analysis was 0.85 (95% CI: -0.28 to 1.99) in percentage change. The slope was 0.02 (95% CI: -0.012 to 0.054) in tumor size change in mm. The slope was not significantly deviated from zero by percentage change (p = 0.14) or size change in mm (p = 0.21). The median time of microadenomas remained unchanged were 6.5, 7.7, and 6.5 years in total, male and female respectively. There was no significant difference in size change among total, male and female (p = 0.947). CONCLUSION: Our study has shown that majority of pituitary microadenomas remain unchanged or decreased in the size over 15 years. The maximal size increase was 6 mm. There were no significant changes in tumor size over the study period. Our study suggests that less frequent surveillance pituitary MRI in incidental pituitary microadenomas is safe. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.