Brain metastases are secondary brain tumours caused by the hematogenous spread of cancer cells from a primary tumour to the brain. With an incidence of 10–30% among all patients with cancer, they are the most common intracranial tumours in adults and occur considerably more frequently than primary brain tumours.
Brain metastases may present as solitary lesions, oligometastatic disease (2–4 lesions), or multiple metastases (5 or more lesions).
They preferentially develop at the grey–white matter junction, where blood vessels narrow and circulating tumour cells may become lodged. Leptomeningeal metastasis (dissemination to the meninges) may also occur and represents a distinct clinical manifestation requiring its own therapeutic strategy.
Brain metastases often develop at a time when patients are not yet substantially impaired by their underlying primary malignancy.
Today, brain metastases are frequently detected while still asymptomatic during imaging performed as part of oncological follow-up. When symptoms occur, they result from the mass effect of the tumour, peritumoral cerebral oedema, or direct injury to brain tissue.
The diagnostic work-up for suspected brain metastases is aimed at accurately characterizing and localizing all intracranial lesions while also assessing the systemic tumour status. These findings provide the basis for an individualized treatment decision.
The treatment of brain metastases is multimodal and is determined individually within an interdisciplinary tumor board. Key factors include the number, size, and location of the lesions, the primary tumor, systemic disease status, the patient’s general condition, and the molecular characteristics of the tumor.
Stereotactic radiosurgery (SRS) is now a standard-of-care treatment for brain metastases in the oligometastatic setting. The ERCM uses two complementary systems: CyberKnife®, a robotically guided linear accelerator, and ZAP-X®, a gyroscopic radiosurgery system specifically developed for intracranial indications.
Before radiosurgery is initiated, comprehensive staging (brain MRI, CT of the chest/abdomen/pelvis, and PET/CT where indicated) is essential to identify additional metastatic disease and optimize the overall treatment strategy. The number of intracranial lesions is an important factor in determining the most appropriate treatment approach, including radiosurgery versus whole-brain radiation therapy.
ZAP-X is an innovative, fully self-shielded radiosurgery system developed specifically for intracranial tumors. Its gyroscopic design allows the linear accelerator to rotate along a spherical trajectory around the patient’s head and precisely converge radiation from hundreds of angles on the target. This enables a highly conformal dose distribution with an exceptionally steep dose gradient while minimizing exposure of adjacent critical brain structures.
Left: In this case of a patient with breast cancer, a single (singular) brain metastasis occurred – surrounded by edema and critically located in the central region of the brain, which is responsible for motor functions, among other things.
Right: The radiosurgical treatment effectively eliminated the brain metastasis, but it was no longer detectable in the MRI 22 months after the CyberKnife therapy (treatment duration: 25 minutes). The fluid accumulation (edema) had also completely decreased.
In radiosurgical treatment, the entire metastasis is treated, the metastases scar and recede.
Yes, CyberKnife and ZAP-X are effective methods for the treatment of single or multiple brain metastases. Their size and location play an important role in the treatment decision.
Treatment of recurrences depends on various factors, including the number and size, the patient's general condition, and the therapy previously used. Often, re-radiosurgery with the CyberKnife or ZAP-X can be considered, especially if the metastases are small and well defined.
The speed at which brain metastases grow and spread can vary. It depends on various aspects, including the original cancer and also the aggressiveness of the metastases. Some can develop quickly, while others grow slowly. Regular imaging and medical monitoring are therefore very important to detect such growth in time and treat brain metastases.
Depending on their location in the brain, the metastases can also lead to changes in character or changed behavior.
The therapy is usually carried out as a one-time treatment session, especially in the case of small brain metastases. The high precision of the robotic systems makes it possible to concentrate a high dose of radiation on the metastases while sparing the surrounding healthy tissue.
This also depends, among other things, on the location of the brain metastases in the brain, and dizziness or headaches can occur in general.
Rehabilitation is not required after treatment with the CyberKnife or ZAP-X system.
Driving should be avoided due to the risk of seizures in the presence of brain metastases.
Whether you have a solitary brain metastasis, multiple lesions, or a recurrence after previous treatment, the team at the European Radiosurgery Center Munich will review your case individually and advise you on the options for stereotactic radiosurgery with CyberKnife and ZAP-X.