Lung cancer is the second most common type of cancer worldwide, with more than 2 million new diagnoses each year. Small cell lung cancer (SCLC), sometimes called oat cell cancer, makes up between 10 and 15 percent of all lung cancer cases.

SCLC tends to spread more aggressively than the more common non-small cell lung cancer (NSCLC). In fact, for about 70 percent of people with SCLC, it’s already spread to another part of their body by the time it’s been diagnosed. When lung (or any other) cancer spreads to another part of your body and grows there, it’s called metastasis.

If you detect SCLC while it’s only in one lung and before it’s metastasized elsewhere, it’s called limited SCLC. If it’s spread to both lungs or metastasized somewhere else, it’s called extensive SCLC. Most of the time, SCLC is already extensive by the time you spot it.

But can SCLC spread to your brain? The short answer is yes. This is actually common with SCLC. Read on to learn more about how SCLC spreads to the brain and what you can expect as a result.

There are two different routes that SCLC can take to reach your brain.

The first is your lymphatic system. This system runs throughout your body and helps filter out things your body doesn’t need, such as damaged cells or bacteria.

The second route is your circulatory system, which includes your veins and arteries and is responsible for moving blood and oxygen around your body.

In both cases, little pieces of the primary tumor in your lungs break off. These pieces can enter your lymphatic or circulatory systems and use them to travel throughout your body.

The cancerous cells later exit these systems and can continue growing wherever they end up, including in your brain. This is called brain metastasis.

Even though the tumor is in your brain, it’s not brain cancer. Because the cells came from your lungs, it’s metastatic lung cancer in your brain.

Your brain is highly complex, and there are many places within it where metastasis might occur. Your symptoms will depend on how many metastases you have and where in your brain they’re located. It’s possible (but uncommon) that you won’t have any symptoms.

The most common symptoms of brain metastasis include:

SCLC is usually treated with chemotherapy and radiation, often together. But if SCLC has spread to the brain, chemotherapy may not be as effective.

If brain metastases are found, treating them will likely take priority over treating other locations. Your doctor may treat the symptoms of brain metastases, such as seizures or swelling, with antiseizure medication and steroids until they can address the metastases directly.

Radiation is the main treatment for SCLC brain metastases. The type of radiation you receive will depend on your unique circumstances.

  • Whole-brain radiation therapy (WBRT) is the standard treatment. Your doctor might use WBRT if you have a large number of metastases.
  • Stereotactic radiation is a more targeted, higher-dose treatment than WBRT. Doctors sometimes use it in conjunction with surgery.
  • Prophylactic cranial irradiation (PCI) is treatment for your brain with the goal of preventing brain metastasis. After other forms of radiation, your doctor may recommend PCI to prevent a relapse. They may also proactively recommend PCI if you have limited SCLC.

Radiotherapies can be effective treatments for brain metastases, but they can also damage the healthy parts of your brain. This can cause neurological symptoms, such as impaired spatial learning and working memory. You’ll want to talk with your doctor to help you weigh the risks against the potential benefits.

Lung cancer is the most common cause of cancer death worldwide in both men and women. Once SCLC has reached the brain, long-term survival rates are poor. After brain metastasis, the 5-year survival rate is less than 2 percent.

For people in poor health overall, chemotherapy and radiotherapy treatments may be too strenuous to safely administer. In these cases, doctors may recommend palliative care to provide physical and emotional comfort.

How likely is it that small cell lung cancer will reach the brain?

Between 10 and 20 percent of people with SCLC already have brain metastases when they receive their diagnosis. Between 50 and 80 percent of people with SCLC will experience brain metastasis during treatment.

How quickly can SCLC spread to the brain?

For people whose SCLC hasn’t reached the brain at the time of diagnosis, brain metastasis typically occurs within 10 months. This generally takes longer for people with limited SCLC, and a little more quickly for people with extensive SCLC.

Are there any emerging treatments for SCLC brain metastases?

There are several active clinical trials to evaluate treatments for brain metastases in people with SCLC. For a current list, you can search

Clinical trials are currently investigating treatments, including:

  • immunotherapy combined with chemotherapy
  • stereotactic radiosurgery
  • avoiding the hippocampus when using radiation
  • comparing preventative and delayed radiation treatments
  • alternating electrical fields

Of the two types of lung cancer, SCLC is less common but more aggressive. SCLC is classified as extensive when it has spread beyond one of your lungs. Most people with SCLC are already in the extensive stage when they receive a diagnosis.

When the cancer spreads, it frequently goes to your brain, where it metastasizes. While chemotherapy is usually the first line of treatment for SCLC outside of the brain, radiation is usually the main treatment for brain metastases.

When talking with your doctor about treatment options, ask about comfort and quality of life in addition to survivability rates.

If you believe you might be at risk for lung cancer, ask your doctor what preventative steps you can take to lower your risk. The earlier you can identify that you have SCLC, the better. If you think you might have SCLC, you should make an appointment with your doctor right away.