Most people understand that tobacco use is the number one cause of lung cancer, and therefore, that lung cancer is more prevalent among smokers. However, what many people don't know about lung cancer is that it has two main types: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
Non-small cell lung cancer accounts for about 90% of lung cancer diagnoses¹ and often has a slower growth rate than small cell lung cancer. NSCLC also develops relatively slowly, with few or no symptoms until it advances.
In this article, however, we will discuss small cell lung cancer.
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Small cell lung cancer is a rapidly spreading and aggressive type of lung cancer that forms in the lung tissues. It advances so rapidly that the disease may have spread outside the lungs before you even receive a diagnosis. It also has a high chance of returning after treatment.
Small cell lung cancer is also commonly referred to as oat cell cancer because it causes small, oval-shaped cells that resemble oat grains under magnification.
This cancer usually begins in the bronchi or air passages that channel air into the lungs from the trachea and then splits into small progressive structures. Once it affects the bronchi, it grows quickly and spreads to other body parts such as the lymph nodes, liver, and brain.
SCLC typically occurs on its own; occasionally, it can occur in combination with a non-small cell subtype.
SCLC may be asymptomatic in very early stages but grows rapidly to cause various symptoms².
Symptoms may include:
Chest pain or discomfort
Recurring cough or hoarseness that doesn’t dissipate
Shortness of breath
A loss of appetite
Facial swelling from blockage of a large blood vessel in the chest
Neurological symptoms due to cancer spreading to the brain or the spinal cord.
You should speak to your doctor if you experience such symptoms. While they may not mean that you have SCLC, early diagnosis means more treatment options will be available.
SCLC diagnosis starts with physical tests and medical history. Those who smoke should tell their doctor. If you suspect SCLC, the doctor can use different tests to help detect SCLC.
After diagnosing it, the doctor can move on to determining the stage of this cancer. However, more often than not, SCLC symptoms do not appear until the cancer is in the advanced stage.
Your doctor can detect SCLC through tests such as:
This may be the first test your doctor orders, prior to proceeding to other, more sophisticated tests.
CT scan and PET scan
A CT scan produces multiple cross-sectional X-ray images of the lungs and the rest of the body to assess the degree of spread. A PET scan relies on the uptake of labeled glucose by cancer cells to assess the degree of spread.
An MRI scan of the brain is usually done to exclude the spread of cancer to the brain.
This involves the insertion of a tube with a camera and light to examine the lungs and other structures. A biopsy may also be performed and is required to confirm the diagnosis of small cell lung cancer.
If you are at a high risk of developing lung cancer, your doctor may recommend that you take screening tests. You are considered to be at high risk if:
You smoke over 20 packs of cigarettes each year,
Are between 50 and 80 years old, and
You currently smoke or have quit smoking in the last 15 years.
Staging describes the extent of the spread of cancer and can help the doctor determine the treatment options and outlook.
The stages of small cell lung cancer³ include:
1. Limited stage lung cancer
The limited stage is cancer confined to one side of the chest. It may also affect the lymph nodes on one side. One out of three people is at this stage when they receive their first diagnosis.
2. Extensive stage lung cancer
During the extensive stage, cancer has already spread to other sites. If these cells are present in the fluid that surrounds the lungs, the cancer is considered to be in the extensive stage category, even if it is confined to one lung. Cancer at this stage becomes difficult to treat. Two out of three people are at the extensive stage when diagnosed.
SCLC develops and spreads faster than non-small cell lung cancer. And it's for that reason that people with an increased risk of contracting this cancer, such as smokers, should undergo annual screening¹.
Cancer cells arise from damage to the DNA. DNA carries the code for the cell to function properly. Once DNA is damaged, the cell and its components may not function properly. They then grow uncontrollably and spread to other parts of the body.
Smokers are at a higher risk of developing SCLC, and almost everyone diagnosed with SCLC is a smoker. It is a rare condition in non-smokers. The number of cigarettes you smoke every day and the duration you have been a smoker have a direct correlation with risk. Therefore, long-term smokers who consume more cigarettes in a day are at a higher risk of developing the disease⁴.
The popular belief is that smoking light or low tar cigarettes is less risky. That is, you are not at risk of developing lung cancer if you smoke them over standard cigarettes. However, menthol cigarettes may, in fact, put you at a higher risk of developing small cell cancer since menthol may allow a deeper inhalation of the smoke. If you smoke cigars and pipes, you may also be at a higher risk than a person who smokes cigarettes.
It’s not only smokers who are at risk; frequent exposure to secondhand smoke either at home or work is unhealthy and increases the chances of developing this disease by 20-30% for non-smokers¹.
There are other carcinogenic substances that can put you in a higher risk category if exposed to them:
Radon, a radioactive gas present in the basements of some homes
Asbestos, a building material present in many older buildings and homes
Drinking contaminated water (water containing arsenic)
Inhaled chemicals, like silica, arsenic, and coal products
Diesel exhaust and outdoor air pollution
Some dietary supplements, like beta carotene
Radioactive substances such as uranium.
Treating small cell lung cancer as early as possible is critical to increasing the chances of favorable results. But once the cancer advances, the treatment may no longer be curative.
Except in the very early stages of SCLC where cancer has not spread to adjacent lymph nodes, surgery is not an option for most patients diagnosed with small cell lung cancer. Your surgeon may remove the lobe of the lung that contains cancer.
Adjacent lymph nodes will be examined during surgery to ensure no spread has taken place. You will likely need chemotherapy following surgery.
Chemotherapy and immunotherapy
Chemotherapy in combination with radiation is the mainstay in treating limited-stage SCLC. Despite its curative potential, a large number of patients will relapse following successful completion of initial treatment with chemotherapy and radiation.
In extensive-stage SCLC, chemotherapy in combination with immunotherapy is the current standard of treatment. Although cancer responds well to treatment initially, it often comes back and no longer responds to treatment as well.
The side effects of chemotherapy include⁵:
Nausea and vomiting
A drop in blood cells, with a risk of severe infection
Skin changes (rash)
Loss of appetite
Hearing loss or ringing in the ears (tinnitus)
Radiation therapy or radiotherapy
Radiation therapy applies concentrated radiation beams to destroy cancer cells.
In limited-stage SCLC, chemotherapy combined with radiation is the current standard of care. Following completion of treatment, you may receive prophylactic radiation to your brain to reduce the risk of cancer spreading to the brain.
In extensive-stage SCLC, radiotherapy is only used in select situations, such as a painful cancer spot in a bone.
SCLC is an aggressive type of cancer. Even with limited-stage cancer and curative intent of treatment, there is a high risk of cancer coming back.
On average, the five-year survival rate for patients with early-stage, localized SCLC is about 27%. In contrast, extensive-stage SCLC patients have a five-year survival rate of about 3%. Overall, the average five-year survival rate for SCLC is about 7%⁶.
Small cell lung cancer is an aggressive form of lung cancer characterized by the fast and uncontrolled growth of particular cells in the lungs. It develops faster than other types of lung cancer, and most individuals get their diagnosis once it has already spread.
People with a higher risk of developing SCLC, like those who have been smoking for a long time, should speak to their doctor to see if screening is appropriate for their situation.
Lung Cancer Fact Sheet | American Lung Association
Lung cancer - Symptoms | NHS
Small Cell Lung Cancer Stages | American Cancer Society
Small Cell Lung Cancer Causes, Risk Factors, and Prevention | American Cancer Society
Chemotherapy Side Effects | American Cancer Society
What is the life expectancy for small cell lung cancer? | Medical News Today
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