If lung cancer isn’t caught early, there’s a high risk of it spreading to other parts of your body, including the brain. When cancer cells travel to the brain, doctors call it brain metastases (or brain mets).
This can cause one or more tumors to form in the brain, which can lead to serious symptoms like blurry vision, slurred speech, headaches, and seizures. Brain mets are common in lots of different types of cancer, but they’re especially common in lung cancer. About 50% of those who have lung cancer will develop brain mets. And around 25% already have them at the time of diagnosis.
If you have metastatic lung cancer, odds of survival are poor. But for those who develop brain mets, the outcome might be worse. On average, most people with brain mets survive less than 6 months after diagnosis.
Lung Cancer and the Brain: What’s the Link?
If lung cancer isn’t caught early, the cancer cells can spread through lymph nodes and the blood supply to different parts of the body, including the brain. In fact, most brain mets start out as lung cancer. What’s the link? Experts don’t fully understand it.
Some recent research on mice shows that when lung cancer cells travel to the brain, they quickly build blood vessel branches. This gives them the blood supply to survive and multiply. Some studies point out that nicotine from cigarette smoke might play a role. But experts say they need to research and study the link more.
The lung cancer with the highest risk of brain mets is small-cell lung cancer (SCLC). You can also develop brain mets with some forms of non-small-cell lung cancer (NSCLC) caused by changes (or mutations) in certain genes, such as:
- EGFR-positive lung cancer
- Anaplastic lymphoma kinase (ALK) positive lung cancer
- (ROS1)-positive NSCLC
According to research, about 50% to 60% of people with EGFR- or ALK-positive lung cancer go on to develop brain mets. Why is this? Doctors aren’t sure. But those who have NSCLC tend to live for several years after they’re diagnosed. Experts believe that this might allow the cancer more time to spread to the brain. Other theories suggest that targeted treatments for lung cancer might not properly reach the tumors within your brain. Or these mutation-based cancer cells might have a genetic tendency to travel to the brain.
Brain mets that grow inside your brain matter are the most common type. But in some cases, cancer might spread to the fluid around your brain. This is called leptomeningeal disease (LMD).
What Are the Symptoms of Brain Metastases?
Brain mets can be microscopic and cause no symptoms initially. Symptoms related to brain mets depend on the location and size of the tumors in the brain. Symptoms also reflect how quickly a tumor is growing and if there is actual increased pressure within the brain. Symptoms may reflect the impact of brain mets on the local brain tissue (focal) or affect brain function (global) from increased pressure and swelling inside the brain. You’re also more likely to have global symptoms if you have leptomeningeal disease as well.
Focal symptoms result from direct pressure or destruction locally in the brain. This is often from tissue destruction from the tumor, or from a stroke into the tumor, or from a seizure caused by the tumor. They can include:
- Weakness on one side of your body
- Numbness or tingling on one side of your body
- Slurred speech
- Vision changes
- Problems walking
Global symptoms include:
- Headaches. This may happen in the morning when you wake up after lying down all night.
- Confusion or memory problems
- Nausea and vomiting
- Personality changes
The symptoms may suddenly change if you have a bleed (hemorrhagic stroke) from the tumor. Bleeding inside the brain is a medical emergency that often requires surgery to control. This may not be possible in the case of bleeding from brain mets.
How Is Brain Metastasis Diagnosed?
Your doctor will run a few tests and exams, such as:
Neurological exam. Your doctor will check for many brain-related functions such as:
Imaging tests. A MRI scan with contrast dye might help your doctor find brain tumors. The dye is an injectable ink that’s given into your arm. During the scan, the dye will make the tissues and blood vessels in your brain show up more clearly and have a lot more detail.
Other imaging tests may include:
- CT scan. In some cases, your doctor might find brain mets before they diagnose you with lung cancer. If your doctor thinks the tumor traveled from the lung, they can order a chest CT scan to look for signs of cancer.
- PET scan (positron emission tomography)
If your doctor finds brain mets, you’ll likely be followed regularly with repeat imaging studies. The time period between studies will vary and depends on the size and growth of the tumor.
Biopsy. If your doctor finds a mass or a tumor, they may recommend taking a small sample with a needle to make sure that it is metastatic lung cancer. This is called a biopsy. A lab technician will see the sample under a microscope to check whether the cells are cancerous (malignant) or noncancerous (benign). They can also tell whether cancer cells came from some other part of your body (brain mets) or grew in your brain (the primary tumor).
If leptomeningeal disease (LMD) is suspected, your doctor will insert a long needle between two vertebrae in the lower part of your spine and take a fluid sample. This procedure is called a lumbar puncture. They then check the fluid to see if it has cancer cells from the lung.
How Is It Treated?
If your lung cancer spreads to your brain, there are several treatment options. These include:
Medications. Some cancer drugs come in pills that you can take by mouth, while others are given intravenously (IV) in a vein. The type of medications your doctor recommends will depend on the locations of your brain lesions and your individual situation.
Chemotherapy. This kills cells that grow quickly, including cancer cells. If you have LMD, your doctor might inject chemo into your arm or directly into your spinal fluid. They can also give it through a device that’s inserted under your scalp called an Ommaya reservoir.
Targeted therapy. If you have brain mets caused by lung cancer that have certain genetic biomarkers like ALK and EGFR, then you might get this therapy. Targeted pills focus on flaws within cancer cells and block them. This causes cancer cells to die.
But you might have to wait a few weeks before your doctor can confirm whether your cancer has biomarkers. If you need to start treatment as soon as possible, you might have to rule out this option.
Focused radiation to the brain. Also called stereotactic radiosurgery, this therapy uses radiation beams in a specific way to kill cancer cells in the brain. For the procedure, your doctor may use machines called Gamma Knife and Cyberknife to attack cancer cells.
Whole-brain radiation therapy (WBRT). This therapy uses radiation beams on your entire brain. But sometimes, your doctor might shield the hippocampus – the part of the brain that controls memories – during the procedure to prevent memory problems. This is called “hippocampus sparing.”
WBRT may also be done if you have SCLC before cancer can spread to your brain because SCLC has a high risk of brain mets, including microscopic brain mets. This procedure is called prophylactic cranial irradiation. But because this can cause serious side effects, your doctor might just closely monitor your brain for metastatic tumors with regular MRIs.
Neurosurgery. If the brain met is too large or starts to cause symptoms, your doctor might perform surgery to remove the affected area. They may follow this up with radiation in the same area after surgery.
What’s the Outlook?
If your lung cancer spreads to the brain, research shows that the outlook is poor. On average, those who develop brain mets tend to live for less than 6 months after diagnosis.
Because brain tumors can affect areas of the brain that control your motor skills, speech, hearing, balance, or memory, after treatment you might need rehabilitation as part of your recovery process. This can include therapies like physical therapy, occupational therapy, and speech therapy. Your doctor might refer you to an expert after you finish treatment.
If treatment options are not able to work well enough to fight back cancer, your doctor might suggest supportive care like hospice and palliative care. These therapies are provided by a team of experts who work with you and your loved ones to support you physically, emotionally, and spiritually to help improve your quality of life as you live with advanced lung cancer and brain mets.