MRI May Not Detect Pituitary Tumors in Young Patients

Margarida Maia, PhD avatar

by Margarida Maia, PhD |

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A technician readies a patient to have an MRI scan.

MRI scans may fail to detect a disease-causing pituitary tumor in up to one third of children and adolescents with Cushing’s disease, a study found.

In the study, patients with a negative MRI scan result were less likely to enter in remission after having surgery to remove the pituitary tumor than those who had a positive MRI scan result. However, for patients who went into remission, the risk for long-term recurrence was not linked to MRI scan results.

These findings may be of value for doctors who provide informed counseling to patients and their families prior to surgery.

The study, “Paediatric patients with Cushing disease and negative pituitary MRI have a higher risk of nonremission after transsphenoidal surgery,” was published in the journal Clinical Endocrinology.

Cushing’s disease is a form of Cushing’s syndrome that occurs when the brain’s pituitary gland makes too much adrenocorticotropic hormone (ACTH), generally due to the presence of benign pituitary tumors called adenomas.

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The first treatment choice for Cushing’s disease is transsphenoidal adenomectomy, a surgery in which the pituitary tumor is removed with minimal damage to surrounding structures. A surgery to remove the entire or part of the pituitary gland, called a hypophysectomy, may be performed as an alternative in some cases.

While pituitary imaging often is performed to look for the root cause of Cushing’s disease, in young patients pituitary adenomas may be too small to be detected by MRI scans.

To understand the likely outcome of Cushing’s disease in children and adolescents with negative MRI findings, a team of researchers in the U.S. analyzed clinical data of 186 patients who received a diagnosis at a mean age of 13.3 years. They were part of a much larger, ongoing study (NCT00001595) focused on assessing the variety of tumors found in the pituitary gland of pediatric patients.

Of the 186 patients, 127 (68%) had a pituitary adenoma detected by MRI. The other 59 (32%) had a negative or inconclusive MRI result.

“Consistent with previous studies, … MRI results may be negative in up to one‐third of patients,” the researchers wrote.

Patients with a negative MRI result were younger at the time of diagnosis than those who had a positive MRI result (median age of 11.1 vs. 14.4 years). They also had lower morning levels of ACTH and cortisol — a hormone produced by the adrenal glands in response to ACTH. 

For patients with a negative MRI result, tumor size — calculated after surgery — was 20% smaller than for those who had a positive MRI result.

Among the 181 patients with data on the postoperative course, 27 (15%) did not achieve immediate remission, or ceased having signs and symptoms of the disease for a time, after having their first surgery.

Sometimes, the first surgery leaves behind some tumor tissue, making a second surgery necessary. In the study, 11 of the 13 patients who underwent a second surgery within three weeks of the first one achieved remission.

Patients with a positive MRI scan result were 2.6-times more likely to achieve remission after having their first surgery compared with those who had a negative MRI result.

Yet, for patients who achieved remission after the first surgery, the risk for long‐term recurrence was not linked to the detection of pituitary tumors in preoperative MRI scans.

“A negative MRI appears to signal an overall higher risk for nonremission,” the researchers wrote. However, if transsphenoidal adenomectomy “is successful in cure early on, then the long‐term risk for recurrence is not dependent on the preoperative imaging findings,” they wrote.