Gamma Knife stereotactic radiosurgery
for pituitary adenomas

The adjunctive treatment of choice
When additional management (adjunctive treatment) is needed after pituitary adenoma surgery, Gamma Knife stereotactic radiosurgery is often the adjunctive treatment of choice.
When used after primary traditional surgery, Gamma knife adjunctive treatment often returns the patient back to normal hormone function, which is the treatment goal.
Gamma Knife radiosurgery targets the pituitary tumour without damaging adjacent structures. Its primary goal is to:
- Bring the affected pituitary hormone back to their normal or target levels
- Shrink the tumour
- Prevent any further tumour growth
How Gamma Knife radiosurgery works
Pituitary adenomas are benign tumours that may cause symptoms in one of two ways:
- Secreting hormones (growth hormone, adrenocorticotropin hormone or prolactin) or
- Pressing on important brain structures (local mass effect such as chiasmatic compression)
For this reason, the objective of Gamma Knife treatment can either be to:
- Control signs of hormone over-secretion or hypersecretion (for instance in a secreting microadenoma) or
- Decrease tumour volume (for instance in a large non-secreting pituitary adenoma).
While Gamma Knife radiosurgery is a safe and effective therapy, in selected patients with pituitary adenomas, as with all treatments, Gamma Knife treatment can present risks. These include the fact that results with Gamma Knife are not immediate. Medicines may be needed while the tumour and hormones settle down.
Internationally proven treatment
In patients with pituitary adenomas that secrete hormones, Gamma Knife radiosurgery is used when:
- Traditional surgery fails to bring hormone levels back to normal levels and/or
- Medications are unable to control hormone levels or when they cannot be used for medical reasons, such as toxicities.
Following Gamma Knife treatment, hormone levels decline slowly. It may take time (months to years) to slowly bring hormone levels back to the normal, target levels.
Despite this delay, after Gamma Knife treatment, the majority of patients will eventually have the excess pituitary hormone secretion corrected and have normal hormone levels.
A study has revealed that five years after Gamma Knife radiosurgery adjunctive therapy, tumour growth control was 94% and after 10 years it was 83%.
Treatment with Gamma Knife stereotactic radiosurgery
In some cases where traditional surgery is contraindicated or impossible, Gamma Knife radiosurgery may be used as alternative first-line treatment. Hormone control or remission with Gamma Knife has been shown to be:
- 51 % after 5 years
- 69 % after 10 years
- 74 % after 15 years
With Gamma Knife radiosurgery remission is delayed for anything from 12 to 60 months. While the growth hormone slowly returns back to normal, patients may need treatment with medications.
When traditional surgery is followed by Gamma Knife radiosurgery, a patient’s cortisol levels can be controlled.
After traditional first-line surgical treatment, 50 % to 80 % of patients go into remission ie they have normal cortisol levels. When Gamma Knife radiosurgery is used as an additional treatment and within three months of traditional surgery, remission rates in up to half of patients not controlled by traditional surgery is as high as 78 %.
Results of additional Gamma Knife radiosurgery are not immediate. It takes anything from 24 to 36 months to control excess cortisol. During this period when the cortisol is settling down, effective medical treatment will be required to keep cortisol levels within the target range.
First line treatment with medications (dopamine agonists) or traditional surgery is usually excellent. It controls levels in about 90 % of cases.
Gamma Knife surgery may be needed in the 10% of cases that cannot be adequately controlled. Patients who fall into this 10% benefit greatly from Gamma Knife radiosurgery.
Gamma Knife treatment becomes an important alternative for patients when:
- Medication is not tolerated
- Traditional surgery has been unsuccessful
- Traditional surgery is deemed unsafe for the patient