Small cell lung cancer

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 behave differently. About 15% of all lung cancers are small cell lung cancers.

Most small cell lung cancers start in the lung, but they can first be discovered elsewhere in the body - for example, in the brain, bones, or liver. 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.

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 showing 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 lung cancers can sometimes act like miniature glands. They can secrete a range of chemicals and hormones. These substances can be the cause of 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
• nausea and vomiting
• low blood sugars in someone who is not diabetic
• unusual types of muscle weakness
• unusual weight gain or loss
• puffy, rounded face
• 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 neck back to the body. This problem is called superior vena cava syndrome and is a medical emergency. Symptoms include headache, a red or bloated face, and bulging veins in the front of the chest and neck.

Symptoms of small cell lung cancer

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
• fatigue
• difficulty swallowing
• pain in the chest, shoulder, or arm
• bone pain
• hoarseness
• headaches, confusion, or seizures
• swelling of the face, neck, or arms
• noticeable or bulging veins on the chest and neck.

Diagnosing small cell lung cancer

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, and 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-stage cancer occurs only in one lung and nearby lymph nodes.
• Extensive-stage 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.

Expected duration of small cell lung cancer

As with any cancer, even if small cell cancer disappears (goes into remission), there is a chance it can come back.

Preventing small cell lung cancer

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 50 to 80 years who have a 20 pack-year smoking history, who currently smoke or have quit within the past 15 years and are healthy enough to undergo lung cancer surgery. 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.

Treating small cell lung cancer

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, surgically removing the tumor or lung will not be sufficient treatment. Even when all the scans look okay, small cell lung cancer cells often lurk in areas that 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 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 non-small cell lung cancer (the other category of lung cancer), small cell lung cancers are generally not associated with genetic mutations that allow the use of targeted therapies. Targeted 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.

Prognosis

Unfortunately, because small cell lung cancer grows and spreads so rapidly, the outlook is poor. The five-year survival rate is about 9%. 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.

Additional info

National Cancer Institute (NCI)
https://cancer.gov/

American Cancer Society (ACS)
https://www.cancer.org/

American Lung Association
https://www.lung.org/

National Heart, Lung, and Blood Institute (NHLBI)
https://www.nhlbi.nih.gov/

U.S. Environmental Protection Agency (EPA)
https://www.epa.gov/

National Institute for Occupational Safety and Health
https://www.cdc.gov/niosh/