Small Cell Lung Cancer
Medically reviewed by Drugs.com. Last updated on Aug 19, 2020.
What is Small Cell Lung Cancer?
Lung cancers are generally divided into two categories: small cell lung cancer and non-small cell lung cancer. That's because they tend to behavior differently.
Most small cell cancers start in the lung but they can first be discovered elsewhere in the body—for example in the bowel, bladder or prostate. Small cell cancers grow fast and spread quickly, so they are hard to cure. Small cell lung cancer was previously called oat cell cancer because the abnormal cells look like oats under the microscope. This term is not used today.
Blood and lymph move through the lungs as it circulates throughout the body. So, it is very easy for small cell cancer cells to spread very quickly. This kind of cancer can spread to any organ, but most commonly affects the brain, liver, adrenal glands, and bone.
In most cases, by the time it is discovered, it has already reached other parts of the body. Often small cell cancers are in other organs even before it shows up on imaging tests. That's why it can't be cured simply by surgically removing the lung tumor. The standard treatment includes chemotherapy with or without radiation, but in general, not surgery.
Small cell cancers can sometimes act like miniature glands. They can secrete a range of chemicals and hormones. These substances can be the cause problems and symptoms rather than cancer itself. Doctors call this paraneoplastic (par-uh-knee-oh-plas-tick) disorder or phenomenon.
Sometimes it is the symptoms of paraneoplastic disorder that make doctors suspect cancer. Examples include:
- Abnormal mineral levels, such as low blood sodium or potassium
- High blood sugars in someone who is not diabetic
- Unusual types of muscle weakness
- Atypical neurological symptoms
Small cell lung cancers often grow very close to the largest and most important blood vessels in the chest. It is not uncommon for a large vein called the superior vena cava to become blocked by a small cell tumor. This hinders blood flow from the head and brain back to the body. This problem is called superior vena cava syndrome and is a medical emergency. Symptoms include headache, a red face, a bloated look to the head, and bulging veins in the front of the chest and neck.
A range of symptoms can suggest small cell lung cancer:
- A persistent cough
- Coughing up blood
- Shortness of breath or wheezing
- Unexplained weight loss or loss of appetite
- Difficulty swallowing
- Pain in the chest, shoulder, or arm
- Bone pain
- Headaches, confusion, or seizures
- Swelling of the face, neck or arms
- Noticeable or bulging veins on the chest and neck
Lung cancer often is discovered on a chest x-ray, where it appears as a gray or whitish area. Other tests, such as computed tomography (CT), magnetic resonance imaging (MRI), and PET scanning can be helpful in determining:
- the size, shape and location of the tumor
- if and where the cancer has spread
- the best place to take samples of the tumor.
One way to check for small cell lung cancer is to examine mucus from the lungs under a microscope. This test requires that a person cough very hard to bring up phlegm. Doctors can also draw fluid from between the lung and chest wall to check for abnormal cells.
Doctors can also take samples of tissue from lymph nodes or suspicious masses using a thin needle. Another test common test is called bronchoscopy. Doctors thread a slender tube with a camera through the mouth into the lungs. Once in place, she or he can look directly at the tumor and take tissue samples.
Because small cell lung cancer spreads so quickly and widely, it is important to check other parts of the body as well. Tests might include a bone scan, bone marrow biopsy, CT or MRI scan of the head and brain. Additional biopsies can help determine how the cancer is spreading.
Small cell lung cancer has two stages:
- Limited cancer occurs only in one lung and nearby lymph nodes.
- Extensive cancer has spread to both sides of the chest or beyond the chest.
For limited stage cancer, doctors may recommend radiation therapy in addition to chemotherapy.
Researchers are studying the genes associated with the development of small cell cancer of the lung. These discoveries may help develop new treatments that target these specific abnormalities.
As with any cancer, even if small cell cancer disappears (goes into remission), there is a chance it can come back.
Smoking greatly increases the chance of developing any kind of lung cancer. About 90% of people who get small cell lung cancer are either current or past smokers. Quit smoking and avoid secondhand smoke.
The U.S. Preventive Services Task Force recommends annual screening for lung cancer with low-dose computed tomography in adults ages 55 to 80 years who have a 30 pack-year smoking history and currently smoke or have quit within the past 15 years. However, it is unclear whether this strategy will be an effective screening test for small cell lung cancers. This type of lung cancer spreads so quickly, it is difficult to know whether early detection will increase the chance of curing the disease.
Small cell lung cancer almost always has spread outside the lungs by the time it is discovered. So, unless the cancer is limited and has not spread at the time of diagnosis, removing the tumor or lung won't be beneficial.
Even when all the scans look okay, small cell lung cancer cells often lurk areas cannot be removed with surgery. That's why combination chemotherapy (with or without radiation) is the main treatment. The earlier stage allows for more intense and effective radiation therapy within a small area.
Small cell lung cancer frequently spreads to the brain, even if there are no spots seen on CT scan or MRI of the brain. That's done because the cancer cells that are present in the brain are often too small to be detected by the scans. Some doctors will advise radiation to the brain to wipe out microscopic cancer cells.
It is extremely rare that small cell lung cancer stays confined to the lungs. But when initial scans do not show any spread, doctors often recommend an attempt to remove the tumor surgically. This works best when the tumor is at the edges of the lung. In most cases, patients also get chemotherapy.
Initial treatment of extensive disease usually includes combination chemotherapy with an immune checkpoint inhibitor.
Unlike the other category of lung cancer, non-small cell lung cancer, small cell lung cancers are generally not associated with genetic mutations that allow the use of targeted therapies. Target therapy specifically treats the mutation that is involved in the growth and spread of the cancer.
When To Call a Professional
If you notice any symptoms suggestive of lung cancer, such as persistent cough, unexplained weight loss, or coughing up blood, see your health care professional as soon as possible.
Unfortunately, because small cell lung cancer grows and spreads so rapidly, the outlook is poor. The 5-year survival rate is about 6%. It is higher when the doctors find and treat the disease in the earlier, limited stage. Even when treatment is successful initially, there is a good chance the cancer will return, often outside the lungs.
Learn more about Small Cell Lung Cancer
National Cancer Institute (NCI)
American Cancer Society (ACS)
American Lung Association
National Heart, Lung, and Blood Institute (NHLBI)
U.S. Environmental Protection Agency (EPA)
National Institute for Occupational Safety and Health
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