Most pituitary microadenomas do not change in size over 5 years of follow-up
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Most adults with incident pituitary microadenomas have no change in size or a decrease in size during a median follow-up of nearly 5 years, according to findings published in Annals of Internal Medicine.
The study’s researchers recommend fewer MRI scans during follow-up to minimize exposure to the contrast agent.
“Pituitary microadenomas are frequently detected as incidental findings on brain images taken for other medical conditions, such as headaches, strokes or falls with head injury,” Le Min, MD, PhD, assistant professor in the division of endocrinology, diabetes and hypertension at Harvard Medical School, told Healio. “Our study revealed that most microadenomas did not grow in size during the study period, and those that did increase in size exhibited slow growth. Given concerns about the potential accumulation of gadolinium within the brain’s dentate nucleus and globus pallidus after repeated exposure to MRI contrast, and with cost-effectiveness in mind, we suggest that patients with nonfunctioning pituitary microadenomas undergo MRI scans less frequently.”
Min and colleagues conducted a retrospective cohort study of adults who had pituitary microadenomas identified at Mass General Brigham hospital from November 2003 to March 2021. Adults with an MRI of the pituitary available in the institution’s research patient data registry and whose diagnosis of a pituitary microadenoma was confirmed in medical records were included. Demographics, medications and pituitary imaging findings were collected. Tumor size was the largest dimension measured in each report.
There were 414 adults diagnosed with a pituitary microadenoma, of whom 237 had only one brain MRI performed (median age, 45 years) and 177 had multiple MRIs performed (median age, 42 years). In both groups, the median maximal tumor size was 4 mm.
Of the 177 adults with data from multiple MRIs available, 63% had no change in microadenoma size during a median follow-up of 4.91 years, 28% had an increase in size and 19% had a decrease in size. Tumor resection was reported for 10 participants, of whom five had corticotroph adenomas, one had a somatotroph adenoma, one had a Rathke’s cleft cyst and three had only anterior pituitary tissue.
In a mixed-model linear regression analysis, the estimated change in pituitary microadenoma size was 0.016 mm per year. However, findings differed in a subgroup analysis where adults were divided into a group with a baseline tumor of 4 mm or less and a group with a baseline tumor larger than 4 mm. In those with a smaller tumor at baseline, size increased by 0.09 mm per year. Conversely, adults with a larger tumor had a decrease in size of about 0.063 mm per year.
Min said the findings were not surprising as they matched observations in his own clinic where patients did not have a significant increase in microadenoma size over time. He said the findings still need to be verified in a prospective clinical study, but the study could be used as evidence when guidelines for pituitary microadenomas are revisited in the future.
“Current guidelines by the Endocrine Society for monitoring pituitary microadenomas was published in 2011,” Min said. “Our study may help to update the guidelines in terms of MRI intervals in patients with incidental pituitary microadenomas.”
For more information:
Le Min, MD, PhD, can be reached at lmin@bwh.harvard.edu.
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Hordejuk and colleagues recently reported on long-term changes in the size of untreated nonfunctioning pituitary microadenomas (adenomas less than 10 mm in maximum diameter) in 177 patients, finding that over time, 44% had no change, 28% had an increase and 19% had a decrease in size with 9% having both an increase and a decrease in size.
In a previous review we found in a compilation of data from 12 previous studies of 229 similar patients that the rates were different, with 83% experiencing no change, 10% experiencing growth, and 7% experiencing a decrease in microadenoma size (Huang W, et al. Pituitary. 2018;doi:10.1007/s11102-017-0856-0). Adding these numbers together for a total of 406 patients, the percentages are 66% with no change, 18% having an increase and 13% having a decrease in tumor size.
A histogram of the amount of size increase in their patients would have been helpful, as Hordejuk and colleagues indicated that the maximum increase was 12 mm and three patients progressed to macroadenomas. Given these new data, I still agree with the recommendations of the Endocrine Society Incidentaloma Guideline that a repeat MRI scan should be carried out 1 year after the initial scan, then every 1 to 2 years for the following 3 years, and gradually less frequently thereafter to detect tumor growth.
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