Lung cancer is the most common cancer worldwide. There are two main types of lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). SCLC accounts for 10 percent to 15 percent of all lung cancer cases.

SCLC occurs when cells in the lungs become cancerous. When this happens, the cells can grow and form tumors inside the lungs, airways, and surrounding tissues. A number of factors can cause the cancer’s growth, including smoking and exposure to chemicals or irritants. The cause of a particular case of cancer is not always obvious.

What Is Small Cell Lung Cancer?

SCLC is an aggressive form of lung cancer, and it grows much faster than NSCLC. Because SCLC is fast-growing, it is often diagnosed in advanced stages. Roughly 70 percent of people with SCLC are diagnosed with extensive-stage disease (cancer that has spread) by the time it is first found.

SCLC affects different cell types in the lung than NSCLC does.

Types of Small Cell Lung Cancer

There are two subtypes of small cell lung cancer: small cell carcinoma and combined (mixed) small cell carcinoma.

Small cell carcinoma is cancer that develops in the epithelial cells that line the airways (bronchi) of the lungs.

Combined small cell carcinoma is diagnosed when a small cell carcinoma tumor also has components of NSCLC. Under a microscope, there are oat grain-like cells, along with other types of lung cancer tumor cells. Combined small cell carcinoma is rare and makes up only 2 percent to 5 percent of all lung cancers.

What Causes Small Cell Lung Cancer?

Small cell carcinoma is almost always caused by smoking, and it rarely occurs in people who have never smoked before. Other substances that irritate the lungs can also cause SCLC. Risk factors include exposure to:

• Secondhand smoke
• Air pollution
• Radiation from cancer treatments or radon in the home
• HIV infection
• Arsenic, asbestos, tar, nickel, or other chemicals

Other factors, such as old age and family history of lung cancer, can put a person at a higher risk of developing SCLC.

Signs and Symptoms of Small Cell Lung Cancer

According to the American Cancer Society, the most common signs and symptoms of lung cancer are associated with respiratory problems, such as:

• Chest pain that gets worse with coughing, laughing, or deep breathing
• Shortness of breath and wheezing
• A persistent cough that may get worse over time
• Coughing up blood or phlegm
• Hoarseness
• Infections, such as pneumonia or bronchitis, that keep coming back

Other general signs and symptoms include:

• Feeling weak or tired
• Loss of appetite
• Weight loss
• Blood clots

If a person’s cancer has spread to other places around the body (in a process known as metastases), other signs and symptoms can develop. These include:

• Yellowing of the skin and eyes (known as jaundice), which occurs when the cancer has spread to the liver
• Bone pain in the back and hips, which occurs when the cancer has spread to the bones
• Swollen lymph nodes, which can develop if the cancer has spread to them
• Nervous system issues (such as dizziness, balance problems, or headaches), which occur when the cancer has spread to the brain

Paraneoplastic Syndromes

In some cases of SCLC, paraneoplastic syndromes can develop. These syndromes are caused by hormones that are released by the cancer itself. Some examples of paraneoplastic syndromes that can develop in people with SCLC include Lambert-Eaton syndrome, Cushing’s syndrome, and paraneoplastic cerebellar degeneration.

Signs and symptoms of different paraneoplastic syndromes can include:

• Slurred speech
• Loss of fine-motor skills
• Difficulty swallowing
• Seizures
• Loss of muscle tone
• Dizziness
• Difficulty walking
• Loss of sensation in the arms and legs
• Muscle weakness

How Is Small Cell Lung Cancer Diagnosed?

If your doctor suspects that you have SCLC, they will run a series of tests to confirm the diagnosis, including imaging and lung-specific tests.

Imaging Tests

The first imaging test your doctor will typically perform is a chest X-ray. An X-ray will show any masses or abnormal areas in the lungs. If something is detected in the chest X-ray, your doctor will likely order other tests to get more detailed images. Other imaging tests might include:

• Computed tomography (CT)
• Magnetic resonance imaging (MRI)
• Positron emission tomography (PET)

Biopsy

Biopsies entail the removal of pieces of lung tissue to be viewed under a microscope. Biopsies help doctors figure out the specific type of SCLC you have. One such biopsy is called needle biopsy using imaging. This involves using imaging guidance to find a nodule or abnormality from which to remove a tissue sample for examination.

Lung Tests

Some tests involve inserting small tubes equipped with cameras into the body to let doctors see inside the lungs and chest cavity and view how much the cancer has spread. These tests include:

• Bronchoscopy — During this test, a thin tube (bronchoscope) is passed through your nose or mouth, down your throat, and into your lungs.
• Mediastinoscopy — This procedure entails inserting a lighted instrument (mediastinoscope) into the space in the chest between the lungs, called the mediastinum.
• Thoracoscopy — Using a thin, flexible tube, equipped with a light and small camera, a doctor looks at the space inside the chest (outside of the lungs).

Blood Tests

Blood tests can help your doctor understand your overall health. If the cancer has spread to other organs, these tests can pick up on abnormalities.

Stages of Small Cell Lung Cancer

After a cancer diagnosis, doctors will figure out if the cancer has spread, and how far, in a process known as staging. Staging in other cancers is traditionally done using the four-stage TNM staging system. Through this system, a person's stage is determined once the cancer is assigned a letter or number to describe the tumor (T), node (N), and metastasis (M) categories. However, the TNM system is not beneficial when staging SCLC. Instead, doctors use a two-stage system that divides cases into either limited stage or extensive stage.

Limited-Stage Small Cell Lung Cancer

Limited-stage SCLC means that the cancer is found on only one side of the chest. In other words, the cancer is only in one lung and may have also spread to the lymph nodes on that side. Doctors will typically diagnose limited-stage SCLC if the area where the cancer is located is small enough to be treated with radiation using only one treatment area. This stage of SCLC can potentially lead to complete remission (the disappearance of all signs of cancer).

Roughly a third of people with SCLC are diagnosed with limited-stage disease when their cancer is first found.

Extensive-Stage Small Cell Lung Cancer

Extensive-stage SCLC is diagnosed when the cancer has spread throughout both lungs, lymph nodes on both sides of the chest, and to other parts of the body. Doctors will also diagnose extensive-stage SCLC if there is cancer in the fluid surrounding the lungs.

Roughly two-thirds of people with SCLC have extensive-stage disease when their cancer is first diagnosed.

Treatments for Small Cell Lung Cancer

Small cell lung cancer treatment can involve surgery, chemotherapy, radiation therapy, and immunotherapy.

Surgery

Surgery can be used to treat limited-stage SCLC, which has not spread to the other lung or throughout the body.

Radiation

Radiation therapy, which uses high-energy beams to kill cancer cells, can be used to treat limited-stage SCLC. Radiation can be given together with chemotherapy in a combination known as concurrent chemoradiation. Radiation can also be used on the brain to prevent the cancer from spreading there, a process known as prophylactic cranial irradiation.

Chemotherapy and Targeted Therapy

Chemotherapy is a standard treatment for SCLC, especially when the cancer has spread throughout the body. Chemotherapy is a systemic treatment that can reach any part of the body through the bloodstream. Chemotherapy can also be combined with radiation therapy or immunotherapy. Examples of chemotherapy drugs include Paraplatin (carboplatin), Cisplatinum (cisplatin), VP-16 (etoposide), and Hycamtin (topotecan).

Immunotherapy

Immunotherapy drugs help activate the body’s immune system to fight cancer. These drugs can be given by themselves or in combination with chemotherapy. One type of immunotherapy, known as immune checkpoint inhibitors, can be used to treat SCLC. Immune checkpoint inhibitors are antibodies that block a protein called PD-L1 found on some cancer cells, which can help boost the immune system. Examples of immunotherapy drugs include Imfinzi (durvalumab) and Tecentriq (atezolizumab).

Palliative Treatment

To relieve symptoms and improve overall quality of life, palliative procedures such as photodynamic therapy or laser therapy can help open up the airways. A procedure known as thoracentesis can be done to remove fluid from the lungs to help you breathe easier.

Small Cell Lung Cancer Outlook

Understanding survival rates can help people with cancer understand their general outlook. The American Cancer Society breaks down the five-year relative survival rates for people with SCLC, with data taken from studies done between 2010 and 2016. Because SCLC is an aggressive form of lung cancer, the combined five-year relative survival rate is 7 percent.

It is important to remember that relative survival rates are an estimation of cases and do not take into account your individual subtype of cancer, age, overall health, or how well your cancer responds to treatment. Lung cancer research also continues to find new treatments, and clinical trials are constantly being performed to improve the quality of life for those with SCLC.

Talk With Others Who Understand

MyLungCancerTeam is the social network for people with lung cancer and their loved ones. Members come together to ask questions, give advice, and share their stories with others who understand life with lung cancer.

Have you been diagnosed with SCLC? Share your experience in the comments below, or start a conversation by posting on MyLungCancerTeam.