Radiation to the Whole Pituitary Compartment Effective at Controlling Cushing’s, Study Contends

Radiation therapy targeting the entire sella — the compartment where the pituitary gland resides at the base of the brain — is effective at controlling Cushing’s disease and should be considered for patients with suspected invasive adenoma tumors, a new study shows.

The study, “Technique of Whole-Sellar Stereotactic Radiosurgery for Cushing’s Disease: Results from a Multicenter, International Cohort Study,” was published in the journal World Neurosurgery.

In patients with Cushing’s disease, excess cortisol levels are caused by a kind of pituitary tumor (adenoma)  that secretes too much adrenocorticotropic hormone (ACTH).

Removing the adenoma using the transsphenoidal approach — a minimally invasive procedure performed through the nose to remove pituitary tumors — remains the first-line treatment for patients with newly diagnosed Cushing’s syndrome. For patients who fail surgery and medical management, stereotactic radiosurgery (SRS) may be used.

SRS is not a surgery in the traditional sense, as it does not require an incision. Instead, SRS uses many focused radiation beams to treat tumors and other problems in the brain, neck and other parts of the body.

While surgery may achieve very good remission rates in patients with an identifiable adenoma, as many as 50 percent of Cushing’s disease patients have no identifiable adenoma on magnetic resonance imaging (MRI) scans. In such cases, surgeons can opt for SRS targeting the entire sella, a procedure called whole-sellar SRS. However, the outcomes of whole-sellar SRS are not fully known.

Researchers conducted an international, retrospective study to analyze the outcomes of Cushing’s disease patients who received whole-sellar SRS.

The study enrolled 68 patients, including 52 who received the procedure for persistent disease, nine whose disease returned after surgery, and seven as their initial treatment.

Patients underwent a type of SRS known as gamma knife radiosurgery (GKRS), which uses small beams of gamma rays to target and treat brain tumors. They were then followed for a mean of 5.3 years.

Whole-sellar SRS was effective at controlling the disease, researchers found. In the five years after receiving the treatment, 75.9 percent of patients achieved a remission. Of those, 86% remained recurrence-free for five or more years.

The mean volume of area targeted using whole-sellar SRS was 2.6 cm³. Researchers discovered that treatment volumes greater than 1.6 cm³ were associated with a shorter time to remission, indicating that targeting a larger portion is more beneficial.

Also, statistical analysis revealed that a reduced dose of radiation was linked to recurrence, suggesting that a higher dose is more advantageous.

Regarding adverse events, 22.7% of patients who underwent whole-sellar SRS developed loss of one or more pituitary hormones.

Researchers also compared outcomes of patients who underwent whole-sellar SRS to those who received adenoma-targeted SRS, of which the latter involves irradiating only the tumor.

Interestingly, there were no differences in remission rate, time to remission, recurrence-free survival, or new endocrine disease development between both groups.

“Whole-sellar GKRS is effective at controlling [Cushing’s disease] when an adenoma is not clearly defined on imaging or when an invasive adenoma is suspected at the time of initial surgery,” the researchers concluded.