When Is Stereotactic Radiosurgery Used For Brain Metastases?

Brain metastases are areas of cancer that have spread to the brain from another part of the body. It is sometimes also referred to a secondary brain cancer, while the original site of the cancer is known as primary cancer.

Treatment depends on several factors, including the number, size and location of the brain metastases, the type of primary cancer and the person's overall clinical circumstances.

Stereotactic radiosurgery (SRS) is one treatment approach that may be considered for selected patients. Despite the word ‘radiosurgery’, SRS does not involve a surgical incision.

Instead, it uses highly focused radiation to target specific areas within the brain while limiting radiation exposure to surrounding tissue.

What is stereotactic radiosurgery?

Stereotactic radiosurgery is a form of highly precise radiation treatment. It uses detailed imaging and computer-assisted treatment planning to deliver radiation to one or more defined targets.

Gamma Knife is one type of stereotactic radiosurgery used for selected conditions affecting the brain. It can deliver precisely focused radiation to a target without requiring conventional open surgery.

The aim is to treat the identified brain metastases while minimising the radiation dose received by nearby healthy brain tissue as far as possible.

When might SRS be considered?

SRS can be considered as a metastatic brain cancer treatment when characteristics are present that make a highly focused method appropriate.

The decision may depend on:

• The number of brain metastases
• Their size and location
• The appearance of the lesions on MRI
• The type and characteristics of the primary cancer
• Whether there are metastases elsewhere in the body
• Previous treatments
• The person's neurological symptoms and overall health
• The expected benefits and potential risks of different treatment options

There is no single number of metastases that automatically determines whether SRS is appropriate. Modern treatment decisions are increasingly individualised, with specialists considering the overall clinical picture rather than relying on one factor alone.

Why does the size of a metastasis matter?

The size of a brain metastasis can influence whether stereotactic radiosurgery is technically suitable and what treatment plan can be safely created.

SRS is designed to treat defined targets with a high degree of precision. Larger lesions may require a different approach, and the location of a metastasis is also important.

For example, specialists need to consider its proximity to sensitive structures and the amount of healthy brain tissue that would be exposed during treatment. Detailed MRI imaging is therefore an important part of assessment and treatment planning.

How many brain metastases can be treated?

SRS was initially associated primarily with treating a small number of brain metastases. However, advances in imaging, treatment planning and radiation technology have expanded its potential use in appropriately selected patients.

The number of lesions alone does not determine whether SRS is suitable. Specialists may also consider the total volume of tumour within the brain, the size and location of individual lesions and the person's wider clinical circumstances.

This means that two people with the same number of brain metastases could potentially have different treatment recommendations.

What happens before stereotactic radiosurgery?

Before treatment, the specialist team reviews the diagnosis and available medical information. A recent MRI scan is usually important for defining the location and characteristics of the brain metastases.

Previous imaging can also help specialists understand how the condition has changed over time. The team will review any previous treatments and consider other relevant medical information.

Where appropriate, SRS may form part of a wider treatment plan involving other specialists and treatments. Once SRS has been selected, detailed treatment planning is undertaken.

Imaging is used to identify the targets precisely and calculate how the radiation can be delivered as accurately as possible.

Is Gamma Knife the same as stereotactic radiosurgery?

Gamma Knife is a specialised technology used to deliver stereotactic radiosurgery to selected targets in the brain. It is important to distinguish the treatment technique from the equipment used to deliver it.

SRS describes the highly precise method of delivering radiation, while Gamma Knife surgery is a dedicated system designed for this purpose. For suitable brain metastases, Gamma Knife can deliver focused radiation without the need for an open surgical procedure.

Why is specialist assessment important?

Brain metastases can present complex treatment decisions. Modern imaging and treatment planning allow specialists to assess whether highly focused approaches such as stereotactic radiosurgery may be appropriate for an individual patient.

A multidisciplinary team may be involved, bringing together expertise from relevant areas of oncology, neurosurgery, radiotherapy and neuroscience.

For patients and families, a specialist consultation can provide an opportunity to understand the diagnosis, discuss treatment options and ask why a particular approach has been recommended.

Explore Queen Square Neuroscience Health Centre to learn more about Gamma Knife and specialist stereotactic radiosurgery for selected complex brain conditions, including brain metastases.