Gamma Knife South Africa

Professional overview

for pituitary adenomas

1. Antisecretory effects of Gamma Knife radiosurgery

1.1 Growth-hormone-secreting pituitary adenomas

After first-line surgical treatment remission rate ranges from 44% to 74%.

When Gamma Knife radiosurgery (GKRS) is used hormone control was 51% at 5 years, 69% at 10 years, and 74% after 15 years.1

In some cases, traditional or open surgery is contraindicated or impossible, results are similar whether GKRS was used as a primary treatment (without surgery) or as an adjunctive treatment (after unsuccessful surgery), making it a possible alternative first-line treatment in cases where there are contraindications to surgery.

One of the main drawbacks of GKRS is that remission takes anything from 12 to 60 months and may need treatment with medications.

1.2 Adenomas and Cushing’s disease

Results following surgery for Cushing’s ranges from 50 to 80%, varying with the type of adenoma. When adjuvant Gamma Knife radiosurgery (GKRS) is applied within 3 months of surgery endocrine remission rates were 78% (p = 0.017).2

As is the case with growth hormone secreting tumours, the main drawback of the technique is the delay to remission, estimated to be 24–36 months, requiring efficacious medical treatment during this period to control excess cortisol signs.

1.3 Prolactin-secreting pituitary adenoma
Medical or surgical remission was reported in about 90% of cases. However, medication (dopamine agonists) is sometimes not tolerated, and in cases of unsuccessful or contraindicated surgery, an adjunctive treatment may be needed. In such cases when Gamma Knife radiosurgery (GKRS) normal prolactin levels were achieved in 82.1% of patients, out of which 46.4% of patient no longer needed medications and 35.7% were controlled with supplemented medication. Growth of the tumour was controlled in in all cases.3

2. Antitumoral effects of Gamma Knife radiosurgery

The 5-year local control rate after SRS is 94% (95% CI: 93.0–96.0%) and after 10-years it was 83.0% (95% CI: 77.0–88.0%).4

3. Adverse effects of Gamma Knife radiosurgery

3.1 The Risk of Hypopituitarism (too little secretion)

Post-SRS hypopituitarism was the most common treatment-related toxicity observed, at 21.0% (95% CI: 15.0–27.0%).

3.2 Optic-nerve Neuropathy
The rate of GK-induced optic neuropathy is estimated to be less than 2% of cases. The risk increases if the target is too close to the optic chiasm and is generally not recommended in such patients.