A precise form of radiation therapy, known as Gamma Knife radiosurgery, produces a low rate of adverse radiation effects and provides good tumor control when used as an upfront treatment strategy in Cushing’s disease patients, an international study suggests.
The study, “Upfront Gamma Knife radiosurgery for Cushing’s disease and acromegaly: a multicenter, international study,” was published in the Journal of Neurosurgery. The work was led by the University of Virginia Health System.
Despite its name, neither a knife nor surgery are involved in Gamma Knife radiosurgery (GKS). Usually performed as an outpatient procedure, GKS uses intense gamma ray beams with pinpoint accuracy to treat brain lesions.
In Cushing’s disease patients or those with high cortisol levels caused by a pituitary adenoma, surgical removal of the tumor, also known as resection, remains the primary therapeutic approach. This is also true for patients with acromegaly — another pituitary disorder that causes overproduction of growth hormones.
However, like with every surgery, there are risks, including nerve and visual system damage.
GKS is often used in Cushing’s disease patients who failed surgical interventions. But to date, few studies have examined the procedure as an effective and safe initial treatment for pituitary adenomas.
“In carefully selected instances, radiosurgery may be used for managing patients with pituitary adenomas in whom resection would entail a high level of risk, and for those refusing resection,” the investigators wrote.
Researchers sought to retrospectively study the effects of upfront, or initial, GKS for patients with Cushing’s disease and acromegaly.
To do so, seven international GKS centers analyzed the medical records of people they had treated upfront for Cushing’s disease or acromegaly. A total of 46 patients were included in the study, 21 with Cushing’s and 25 with acromegaly. In all cases, GKS was performed only after the failure of medical management.
“The reason for taking the patients directly for upfront GKS was either 1) high surgical risk in view of extensive comorbid medical conditions (in 27 patients) or 2) the patient’s choice of treatment (in 19),” the researchers said.
Patients were followed every six months for the first two years, and every one to two years after that.
Results showed that disease-characteristic excessive hormone production stopped in 51% of all studied cases. Five years after GKS, 28% of acromegaly patients and 81% of Cushing’s patients remained in hormonal remission.
In addition, “patients with CD achieved remission earlier as compared to those with acromegaly,” the team wrote.
After radiotherapy intervention, the tumor either remained stable (39%) or was reduced in size (61%).
Nine patients developed a deficiency in pituitary hormone production, also known as hypopituitarism. One patient had oculomotor nerve palsy, meaning he could not move his eyes normally. In addition, six patients had to repeat GKS at 39.5 months, and two had a resection at 27 and 48 months of follow-up.
“GKS can be considered as an upfront treatment in carefully selected patients with [Cushing’s disease] who are unwilling or unable to undergo resection, but it has a more limited role in acromegaly,” the team concluded.