There is no single treatment for metastatic brain tumors. To understand the treatment options, it’s important to consider each one’s role separately. Surgery, radiation therapy, and drug therapy may be considered based on factors such as the condition of the lesion and the status of treatment for the primary cancer. Gamma Knife is one of the options, but it is not suitable for every patient. This article focuses primarily on metastases within the brain parenchyma that are confirmed on imaging, and outlines the characteristics of the disease, the role of Gamma Knife, and follow-up care after treatment. The individual treatment approach is determined by a physician who reviews the images and clinical information. Please use this article as a basis for discussion with your doctor.

What Is a Metastatic Brain Tumor? How It Differs From a Primary Brain Tumor

Metastatic brain tumors differ in origin from primary brain tumors, which arise from the brain itself, and the approach to treatment differs as well.

Metastatic Brain Tumors Are Treated as Lesions Originating From the Primary Cancer

A metastatic brain tumor is a lesion that forms when cancer originating in another organ spreads to the brain. Rather than being diagnosed as a primary brain tumor arising from brain tissue itself, it is diagnosed as a brain metastasis originating from the original cancer (the primary cancer), and treatment is considered on that basis. For example, if lung cancer spreads to the brain, it is treated as a brain metastasis originating from lung cancer.

The type of primary cancer and the course of treatment received so far are factors considered when determining treatment approaches, including drug therapy.

Common Cancers That Can Spread to the Brain, and Symptoms That May Be Seen

Cancers that can spread to the brain include lung cancer, breast cancer, colorectal cancer, kidney cancer, and malignant melanoma, among others. Symptoms depend not on the type of primary cancer but on the location and size of the lesion and its effect on surrounding tissue, and may include headache, seizures, difficulty moving the arms or legs, and changes in sensation, speech, vision, or balance.

Because these symptoms can also result from causes other than brain metastasis, symptoms alone cannot be used to make a determination. On the other hand, a metastasis may also be found on imaging without any clear symptoms being present. If you notice any concerning changes, please consult your physician.

Metastases Within the Brain Parenchyma Are Considered Differently From Those Spreading Along the Meninges

Brain metastases may form within the brain tissue itself (the brain parenchyma) or spread along the meninges, the membranes covering the brain and spinal cord. The nature of the condition and the approach to treatment differ between the two.

This article focuses primarily on metastases within the brain parenchyma that are confirmed on imaging. Which type applies in a given case is determined by a physician based on imaging and clinical information. Next, let’s look at the main factors considered when determining a treatment approach.

Information Reviewed When Determining a Treatment Approach for Metastatic Brain Tumors

The diagnosis of metastatic brain tumor alone does not determine the treatment approach. Brain imaging, the primary cancer, overall health, and prior treatment are all considered together.

The Number, Size, Location, and Surrounding Changes of Lesions Confirmed on Contrast-Enhanced MRI

Contrast-enhanced MRI — using a contrast agent that makes lesions easier to see — is used to closely examine brain metastases. The number, size, and location of lesions, along with surrounding changes such as swelling, are assessed to help determine the approach to treating the brain lesion (local treatment).

The determination is made individually, taking imaging into account rather than relying on the diagnosis or a description of symptoms alone. That said, imaging alone does not determine the treatment approach either.

Type and Characteristics of the Primary Cancer, and the Status of Cancer Outside the Brain

The drug therapy considered may differ depending on the type of primary cancer and genetic changes in the cancer, among other factors. The extent and treatment status of cancer in other parts of the body are also factors in the decision. The order and combination of treatment for the brain lesion and treatment for the cancer throughout the body vary depending on the patient’s situation.

Multidisciplinary Consideration Based on Symptoms, Overall Health, Treatment History, and Patient Preferences

Whether symptoms are present and their nature, the effect on daily life, and any prior surgery, radiation therapy, or drug therapy are also reviewed. When necessary, multiple specialties — such as neurosurgery, radiation oncology, and medical oncology — consider the treatment approach together.

What matters to the patient, as well as personal and work circumstances, are also taken into account once medical suitability has been confirmed. Treatment is not decided by preference alone, but sharing questions and preferences with your physician is still meaningful. Next, we explain the role of Gamma Knife.

What Kind of Treatment Is Gamma Knife? Its Role in Metastatic Brain Tumors

Gamma Knife is one method used to perform stereotactic radiosurgery for metastatic brain tumors. Despite the words “knife” and “surgery” in its name, it is not a treatment that cuts away the lesion.

Gamma Knife Is One Method of Performing Stereotactic Radiosurgery

Stereotactic radiosurgery (SRS) is a form of radiation therapy that concentrates radiation on a target from multiple directions. Gamma Knife is one device and method used to perform SRS, focusing numerous thin gamma-ray beams on the target. For more detail, please see how Gamma Knife works and what the treatment process involves.

Because SRS can also be performed using other devices, SRS and Gamma Knife are not synonymous.

Gamma Knife Does Not Remove the Lesion on the Spot; It Aims for Local Control of the Target Lesion

Gamma Knife does not surgically remove the lesion on the spot; instead, it aims for “local control” of the target lesion using radiation. This refers to the goal of controlling the growth of the lesion or working toward shrinkage, and it is not a guarantee of a cure or of effectiveness. The effect is evaluated over time.

The treatment target is the lesion that has been set as the target. It does not treat cancer elsewhere in the body or lesions within the brain that have not been identified on imaging. Also, SRS being medically considered as an option is not the same as being able to receive Gamma Knife treatment at a specific facility. Next, we outline the situations in which SRS may be considered and the roles of other treatments.

Situations Where Stereotactic Radiosurgery May Be Considered, and the Role of Other Treatments

For metastatic brain tumors, craniotomy, SRS, whole-brain radiation therapy, fractionated stereotactic radiation therapy, and drug therapy may all be considered. No single option is always prioritized; the role each plays differs depending on the lesion, the patient’s condition, and the status of treatment for the primary cancer.

When Stereotactic Radiosurgery May Be Considered, and the Role of Gamma Knife

SRS may be considered when, after evaluating the number, size, and location of lesions, the combined volume of all lesions, the effect on surrounding tissue, symptoms, overall health, and the status of treatment for the primary cancer, it is determined that precisely targeting the lesion with radiation is an appropriate approach.

Gamma Knife is one device and method used to perform SRS. SRS being medically considered as an option is not the same as being able to receive Gamma Knife treatment at a specific facility. Actual suitability is determined based on the lesion, the patient’s condition, treatment history, and the facility’s equipment and policies, among other factors.

When Craniotomy May Be Considered First, and When Stereotactic Radiosurgery May Be Considered for the Area After Resection

When a large lesion is compressing surrounding tissue and causing symptoms, craniotomy may be considered first in order to remove the lesion and relieve the pressure. Surgery may also be considered when tissue needs to be collected for diagnosis. That said, the presence of symptoms alone does not always mean craniotomy will be prioritized.

The area remaining after a lesion has been removed is called the resection cavity. SRS may be considered for this area to help reduce the risk of recurrence at the resection site, but it is not always performed.

When Whole-Brain Radiation Therapy or Fractionated Stereotactic Radiation Therapy May Be Considered

Depending on how the lesions are distributed, whole-brain radiation therapy (whole-brain irradiation), which treats the entire brain, may be considered. Depending on the size of the lesion and its position relative to critical structures, fractionated stereotactic radiation therapy — which delivers radiation with high precision over multiple sessions — may also be considered.

Single-session SRS, fractionated stereotactic radiation therapy, and whole-brain radiation therapy differ in their treatment range and purpose. None of these is always superior to the others.

Combination With Drug Therapy for the Primary Cancer

Depending on the type of primary cancer and genetic changes, among other factors, drug therapy that is expected to also act on lesions within the brain may be considered. In certain circumstances, drug therapy may be given first, while in others, local treatment may be considered first; the order and combination cannot be generalized. When necessary, multiple specialties are involved in this decision.

Whichever local treatment is chosen, follow-up imaging and clinical evaluation after treatment are important. Next, we explain follow-up care after Gamma Knife treatment.

Follow-Up After Gamma Knife Treatment and Managing New Brain Metastases

After Gamma Knife treatment, follow-up continues in order to assess the treatment’s effect and any changes that occur afterward. This includes monitoring changes in the target lesion as well as checking for any new brain metastases.

The Effect Is Evaluated Over Time, and a Lesion May Still Be Visible on Imaging

Because the effect of Gamma Knife cannot be evaluated from imaging taken immediately after treatment alone, follow-up is continued with MRI. A lesion remaining visible on imaging does not, by itself, mean the treatment was ineffective. In addition to shrinkage of the lesion, a stable size is also considered part of the evaluation.

Changes seen on imaging vary from patient to patient. Rather than relying on a single image, the physician evaluates change by comparing it with previous images.

Distinguishing Between Tumor Progression and Imaging Changes Caused by Treatment May Sometimes Be Necessary

On imaging after treatment, a lesion may appear larger or surrounding changes may be observed. This may be related not only to tumor progression but also to a response to treatment or to radiation necrosis. Radiation necrosis refers to a condition in which the treated area or surrounding tissue is damaged as a result of radiation.

These findings can sometimes be difficult to distinguish on imaging alone, so additional testing or comparison with images taken over time may be performed as needed. Making this distinction from a single MRI can be difficult, and evaluation by a physician is required.

For more detail, please see possible side effects and symptoms to watch for after Gamma Knife treatment.

Ongoing MRI and Clinical Follow-Up Are Needed, Including for the Possibility of New Brain Metastases

Because Gamma Knife delivers radiation to the lesion set as the target, new brain metastases may appear elsewhere. The discovery of a new lesion does not, by itself, mean the target lesion did not respond to treatment.

Because changes can be found on imaging even without symptoms, follow-up with MRI and clinical evaluation continues. If a new lesion is found, additional treatment is considered based on its number, size, and location, treatment history, overall health, and the status of the primary cancer. Additional treatment does not always mean Gamma Knife.

If you are considering treatment from overseas, it’s important to confirm in advance how follow-up care will be handled after you return home.

Consulting the Shiga Gamma Knife Center From Overseas

If you are considering treatment from overseas, the process begins before travel, based on brain imaging and clinical information. However, an inquiry alone does not confirm the diagnosis, suitability for Gamma Knife, or acceptance as a patient.

The Process: Confirming What’s Needed and Making an Inquiry

An individual assessment requires brain imaging as well as clinical information, including details of the primary cancer. Because it is difficult to determine a treatment approach from a description of the diagnosis or symptoms alone, please contact us through the inquiry form and confirm with the facility what documents are required and how to submit them. You may also find information to prepare before a consultation helpful.

At the inquiry stage, the diagnosis, suitability for treatment, and acceptance as a patient are not confirmed. In some cases, a treatment other than Gamma Knife may be more appropriate.

What to Confirm in Advance Regarding Follow-Up After Returning Home

Follow-up with MRI and clinical evaluation is needed even after Gamma Knife treatment. It’s worth organizing in advance which medical institution will be responsible after you return home, which physician will review the images, and where to turn if symptoms appear.

Imaging may also be performed at a medical institution in your home country. Please confirm the specific arrangements with both the facility providing treatment and your physician at home.

If you are considering treatment from overseas, please contact us through the inquiry form and confirm with the facility what images and clinical information are needed for an individual assessment, as well as how to submit them. At the inquiry stage, the diagnosis, suitability for Gamma Knife, and acceptance as a patient are not confirmed.

Frequently Asked Questions

Can metastatic brain tumors be treated with Gamma Knife alone?

Gamma Knife is a treatment aimed at local control of the target lesion. It does not treat cancer elsewhere in the body or lesions within the brain that have not been identified on imaging. Treatment is not always completed with Gamma Knife alone, and the physician determines the treatment approach, which may include combination with drug therapy and other treatments.

I’ve been advised to have craniotomy — can this be changed to Gamma Knife instead?

This is not always possible. If a large lesion is causing compression, or if tissue needs to be collected for diagnosis, craniotomy may be considered first. After confirming with your physician why surgery was proposed, the treatment approach is considered based on imaging and clinical information.

A lesion is still visible on my post-treatment MRI — does that mean the treatment didn’t work?

A lesion remaining visible on imaging does not, by itself, mean the treatment was ineffective. A response to treatment, tumor progression, and radiation necrosis can sometimes look similar. Rather than drawing a conclusion from the size of the lesion alone, the physician evaluates this by comparing it with previous images and, if needed, additional testing.

Can new brain metastases appear in areas other than the one that was treated?

Yes, new brain metastases can appear. The presence of a new lesion and any change in the treated target lesion are evaluated separately. If a new lesion is found, additional treatment is considered based on its number, size, and location, as well as prior treatment. Additional treatment does not always mean Gamma Knife.

I live overseas — what should I do first?

Please contact us through the inquiry form and confirm with the facility what images and clinical information are needed, as well as how to submit them. At the inquiry stage, the diagnosis, suitability for Gamma Knife, and acceptance as a patient are not confirmed. It’s also worth confirming, before you travel, where you will receive follow-up care after returning home.

Even if you still have questions about treatment options, you are welcome to contact us through the inquiry form. Individual decisions are made by a physician who reviews the images and clinical information. When you reach out, please confirm with the facility what documents are needed for review and how to submit them.