Use of
Gamma Knife technology for brain metastases

Brain metastases are cancer cells that have spread to the brain. Cells break away from the original tumor and spread to other organs. When that organ is the brain, they are known as brain metastases. In Germany alone, around 40,000 new cases are reported every year. Most commonly bronchial carcinomas (lung cancer), mammary carcinomas (breast cancer), and malignant melanoma (black skin cancer) spread to the brain. In principle, any type of cancer can spread to the brain.

Symptoms depend primarily on the location and size of the metastases. Patients do not usually notice tiny metastases a few millimeters in size. Larger metastases. however. penetrate the surrounding brain regions, compress the brain, and often cause swelling (edema). Symptoms will vary depending on the tumor location: headache, motion and sensory dysfunction, through to epileptic seizures. Personality changes and impaired vision are also possible. Compression of the brain can cause nausea and vomiting, or even unconsciousness.

Metastases in the brain cause death within weeks to a few months if left untreated. Cortisone provides quick relief from acute symptoms caused by swelling of the brain (intercranial pressure). Epileptic seizures triggered by the metastases can be controlled with antiepileptic drugs.

There are four therapy options for treating brain metastases:

1. Microsurgical removal (surgery)
2. Skull irradiation
3. Chemotherapy or immunotherapy
4. Radiosurgery (Gamma Knife)

Any of these procedures may be equally suitable depending on the type, size, number, and location of brain metastases. Hence the best treatment procedure for each patient is determined individually as part of an interdisciplinary tumor conference.

Surgery is required to remove a large, displacing metastasis. Chemotherapy and immunotherapy can at best prevent brain metastases from growing for a certain period, if at all. This is because these substances cannot cross the blood-brain barrier.

Whole brain radiotherapy has one major drawback insofar as it can be carried out only once in a lifetime. It can also cause permanent brain damage. After 6–12 months this may become apparent in the form of cognitive brain dysfunctions (memory impairment, lack of concentration, slowdown, loss of balance). Whole brain radiotherapy is often unable to permanently eliminate highly radiation-resistant brain metastases.

Radiosurgery by contrast provides fairly reliable treatment of all types of brain metastases by applying a concentrated radiation dose with pinpoint accuracy. The radiation exposure is very low and rarely causes side effects particularly with small metastases.

During radiosurgery, we irradiate individual metastases using high-dose radiation. This is important for metastases of malignant melanomas or renal cell carcinomas that are radiation-resistant. These two types of tumors have a higher repair capacity than brain tissue. As a result, whole brain radiation therapy would end up destroying the brain before killing the metastases. Radiosurgery is therefore the method of choice for radiation-resistant metastases.

Radiosurgery as an excellent alternative to whole brain radiation therapy

In the case of individual or a few metastases, radiosurgery is a very good alternative to whole brain radiation therapy. Treating only the metastases does not have any side effects on memory and cognitive functions.

We can now treat up to ten metastases effectively in a single session. However, the prerequisite is a disease that is monitored oncologically. This ensures the oncological therapy (chemotherapy, immunotherapy) keeps the tumor in the body adequately ‘in check’. The patient must also be fit enough to benefit from the treatment.

Cancer requires lifelong checkups. After radiosurgery, we recommend an MRI scan three times a year to examine the brain. To monitor the therapy response and occurrence of side effects. And to detect new metastases early on and be able to repeat the therapy.

Side effects occur in around 10% of patients 4–12 months after treatment. These are usually swellings in the immediate vicinity of the metastasis. These are treated with a short course of cortisone. Asymptomatic reactions to the radiation do not need any specific therapy.

In around 1–3% of cases an uncontrollable swelling occurs which may cause permanent neurological problems. This will then require surgical removal of the destroyed tumor tissue.

It is sometimes difficult to distinguish this kind of reaction to radiation from renewed tumor growth (recurrence) as both look the same on an MRI scan. In these cases, a PET-CT examination provides the answer. We collaborate with the Forschungszentrum Jülich for this examination.