What Happens When Lung Cancer Spreads to the Brain

Lung cancer that spreads (metastasizes) often goes to the brain (brain metastases). People with lung cancer and brain metastases often have questions about what it means for their life expectancy. 

This article will go over the signs and symptoms of lung cancer that has spread to the brain, how it’s treated, and what the outlook is for someone with this type of cancer. 

How Does Lung Cancer Spread to the Brain?

Lung cancer spreading to the brain is fairly common. Up to 7% of people already have cancer cells in the brain when they are first diagnosed with non-small cell lung cancer (NSCLC), and 20% to 40% of those with NSCLC will develop the complication at some point.

About 20% to 40% of patients with non-small cell lung cancer have brain metastases.

Brain metastases occur in stage 4 lung cancer. Once NSCLC is this advanced, life expectancy is usually under a year. 

However, improved diagnostic tools, more effective treatments, and a better understanding of how to manage symptoms have led to a better prognosis for lung cancer with brain metastases. 

It's not possible to say exactly how fast lung cancer spreads, but we do know that small-cell lung cancer spreads faster than non-small-cell lung cancer.

Small cell lung cancer grows quickly enough that around 70% of cases have already metastasized to other areas at the time of diagnosis.

Lung Cancer Brain Metastases Symptoms

Small cell lung cancer is often hard to diagnose in the early stages. It may spread to the brain before a lung cancer diagnosis is even made. 

Non-small cell cancers can also spread to the brain but tend to do so later in the disease after the primary tumor has been found.

Since it's so easy to miss small growths, it's important for people with lung cancer to watch for symptoms of brain metastases.

Symptoms vary based on the type of lung cancer and where tumors are located in the brain, but common symptoms of brain metastasis include:

• Headaches
• Nausea and vomiting
• Seizures
• Speech problems
• Muscle spasms
• Abnormal smells or tastes
• Numbness or tingling in parts of the body
• Fatigue or muscle weakness
• Difficulty with balance or movement
• Vision changes, including loss of vision or double vision

Some symptoms are related to tumors putting pressure on the skull and brain tissue. These symptoms are often worse when first waking up in the morning.

Many people with secondary brain cancer have no symptoms and only find out they have the condition after having a brain scan for an unrelated condition.

Diagnosis

If healthcare providers think that your lung cancer has spread to your brain, they will do imaging tests such as a computed tomography (CT) scan, which uses X-rays to create diagnostic images, or magnetic resonance imaging (MRI), which does the same with magnetic waves

While an MRI is considered more accurate, it cannot be used if you have certain metal implants (including non-safe pacemakers).

If a lesion is found but your provider is not sure what it is, a biopsy can be taken and looked at in a lab to see what it’s made of and whether it is related to lung cancer or something else. 

Leptomeningeal Metastases

Leptomeningeal metastases (leptomeningeal carcinomatosis) are usually late complications of advanced lung cancer. Providers are seeing this condition more often as people with lung cancer live longer. 

Leptomeningeal metastases happen when cancer cells get into the clear, colorless liquid that flows through the brain and spinal cord to bring nutrients to the brain and provide a cushion against injury (cerebrospinal fluid). The cancer cells thrive in this nutrient- and oxygen-rich fluid.

Leptomeningeal metastases are usually linked to many neurological symptoms. It is a terminal stage of cancer with an average survival rate of six to eight weeks.

However, new ways of delivering chemotherapy directly into cerebrospinal fluid have improved the survival rate to between three and nine months.

There have also been some successes with drugs that are traditionally used to target genetic mutations in cancer cells, such as treatments for EGFR-positive lung cancer.

Treatment

Treatments for brain metastases are not considered cures. The goal is to reduce pain and increase how long you can live with lung cancer that has spread to the brain. 

However, that does not mean that these treatments won’t make a positive difference in your quality of life, or even your life expectancy. 

For example, studies have shown that people who are treated with therapy for ALK-positive lung cancer (which is related to a specific gene mutation) with brain metastases have a survival rate of 6.8 years. That's a huge improvement over the estimated 12-month survival rate for lung cancer that has spread to the brain.

The treatment of brain metastases depends on a number of factors including how much of the brain is involved and your overall health. The methods that are used are usually determined by what would be best to help with your symptoms.

For example, steroids such as Decadron (dexamethasone) control brain swelling. Anticonvulsive medications can be used to control seizures.

Before having treatment, your provider will need to figure out if you’re having seizures as a side effect of another treatment or whether an anti-seizure drug might interact with other medications you're taking.

Chemotherapy

Many chemotherapy drugs are not effective at treating brain metastases because they cannot go through the tight network of capillaries that keeps toxins out of the brain (blood-brain barrier).

However, chemotherapy may reduce the size of tumors in the lungs which could limit their ability to spread to the brain.

Targeted Therapy

Targeted drugs for EGFR mutations, ALK rearrangements, ROS rearrangements, and other genetic mutations are sometimes able to go through the blood-brain barrier.

Some newer drugs for EGFR mutations as well as therapies for ALK rearrangements appear to be very effective at treating brain metastases.

Like chemotherapy, these drugs control the primary tumor and limit its ability to spread further.

Immunotherapy

Some immunotherapy drugs are able to cross the blood-brain barrier. If there is only one or just a few brain metastases, immunotherapies can help with the long-term control of cancer.

These therapies are still fairly new, but several medications have shown promise in their ability to reduce brain metastases.

Cancer cells make checkpoint proteins that prevent your immune system from attacking the malignancy, but studies have shown that immunotherapy drugs can stop these proteins, which allows your body to fight cancer.

Whole-Brain Radiotherapy

If scans show that there are multiple brain metastases (as few as four or more than 20, depending on your circumstances), your provider may recommend that you have whole-brain radiotherapy.

This treatment has drawbacks, but it's considered appropriate for people who are at risk for stroke or other serious complications related to brain metastases. It can also be used after surgery to limit the spread of cancer.

With this treatment, the entire brain gets radiation—usually over the course of many weeks. 

Common side effects of brain radiation include memory loss (especially verbal memory), skin rash, fatigue, nausea and vomiting, hearing loss, and seizures.

Radiation oncologists often recommend medication to help with symptoms during treatment. 

While not designed to cure cancer, at least 75% of people who have whole-brain radiotherapy notice some improvement in their symptoms. The treatment has also been shown to improve overall survival from one month with no treatment to two to seven months with treatment

Stereotactic Radiotherapy

Stereotactic radiosurgery (SRS) is a type of high-dose radiation given to a specific area of the brain. Since the radiation is targeted, the side effects are typically less severe. The treatment also tends to offer better survival rates than whole-brain therapy.

When SRS is used to treat body tumors, it is called stereotactic body radiotherapy (SBRT). 

This form of radiotherapy is usually only for people with smaller tumors that are not located too close to the center of the chest where radiation could affect other vital organs.

Proton Therapy

Proton therapy is used similarly to SBRT and is given in an attempt to get rid of brain metastases. 

SBRT is recommended for early-stage tumors or tumors that cannot be surgically removed because of where they're located.

Surgery

Surgery is sometimes an option for brain metastasis if:

• There are fewer than three tumors
• The growths are easily accessed
• There are no other signs of cancer

Surgery can involve the complete removal of a tumor or the partial removal to help with symptoms. Whole-brain radiation typically follows surgery. 

Small-cell tumors are more responsive to radiotherapy alone, so surgery is more often used to remove NSCLC cells.

Palliative Care

The five-year relative survival rates for non-small cell lung cancer and small cell lung cancer that has metastasized to the brain are 7% and 3%, respectively. However, these survival rates can be better for some people thanks to earlier diagnoses and more treatments.

If different treatments are tried and have not helped, you may choose palliative care to help during the final stages of lung cancer. Palliative care can offer relief and reduce the stress of having a terminal diagnosis. 

Palliative care can include the use of pain medications, physical and occupational therapy, or complementary treatments to make you comfortable. These methods do not try to treat or cure cancer, they’re just about improving your quality of life and how you feel. 

You can also choose palliative care sooner than in the final stages of lung cancer, depending on your needs and preferences about treatment. 

Summary

When lung cancer spreads (metastasis) it’s common for it to go to the brain. If you have lung cancer, you should know the signs of brain metastases.

You may have treatment options that could help prevent the spread and help with your symptoms. Treatments mean that even though brain metastasis will affect your life expectancy with lung cancer, you may still be able to improve your quality of life and prognosis.