303 Long-Term Volumetric Analysis of Non-functioning Pituitary Microadenomas: An International, Multi-center Cohort Study

INTRODUCTION: The incidental finding of pituitary microadenomas (PmAs) is increasingly common due to the widespread use of MRI. To date, no comprehensive volumetric analyses of PmAs growth patterns have been conducted. A greater understanding of how these lesions progress could influence an array of management strategies, including frequency of imaging and the use of surgical versus conservative medical intervention. METHODS: Patients who underwent = 2 pituitary MRIs for suspected PmAs were identified retrospectively across 4 referral centers worldwide. Patient demographics, presenting symptoms, clinical variables, MRIs, and treatment course were collected and analyzed. RESULTS: A total of 447 patients (Male = 126; 28.2%) referred to the 4 centers from 2003 to 2022 were identified. Median age at first MRI was 43 years [IQR 32–54]. Median number of MRIs per patient was 3 [IQR 2–5] and median follow-up time was 55 months [IQR 29–100]. 300 PmAs (67.1%) were solid, 102 (22.8%) were cystic, 47 (10.5%) were uncertain, and 24 (5.4%) were mixed. At baseline, median suspected tumor volume was 45 mm3 [15–103]. 77 patients (17.2%) presented with subclinical hyperpituitarism, most often hyperprolactinemia, while 67 (15.0%) experienced hypopituitarism such as hypogonadism, hypothyroidism, and growth hormone deficiency. During follow-up, new onset hyperpituitarism was detected in 20 patients (4.5%) along with hypopituitarism in 9 (2.0%). During the study period, 225 patients (50.3%) had no change in suspected PmA growth, 144 (32.2%) had a decreased size, and 101 (22.6%) had an increased size. 80 patients (17.9%) received medical therapy and 48 (10.7%) underwent transsphenoidal surgery. CONCLUSIONS: With the forthcoming volumetric analysis, we hope to gain further insights into predictors of long-term volumetric evolution of PmAs to improve patient management.