Small Cell Lung Cancer

Small cell lung cancer is a rare, fast-growing type of lung cancer that typically affects people with a history of smoking. While it often spreads quickly, it responds well to treatment initially, though finding better long-term solutions remains a critical challenge for patients and doctors alike.

Table of contents

• What is small cell lung cancer?
• How common is this condition?
• Types of small cell lung cancer
• How small cell lung cancer affects the body
• Symptoms and warning signs
• Causes and risk factors
• Diagnosis and testing
• Treatment options
• Prognosis and outlook
• Prevention

What is small cell lung cancer?

Small cell lung cancer is a disease in which cancerous cells form in the tissues of the lung^[1]. It is a rare, fast-growing type of lung cancer that can affect anyone, but most commonly occurs in people who have a long history of tobacco use, particularly cigarette smoking^[1].

Small cell lung cancer is more aggressive than other types of lung cancer and spreads rapidly throughout the body^[2]. This cancer usually begins in the airways of the lung and quickly spreads to other areas^[2]. Even though this cancer tends to grow quickly, it often shrinks quickly in response to chemotherapy, radiation therapy, or both^[2].

How common is this condition?

Small cell lung cancer accounts for about 15% of all lung cancer cases diagnosed each year^[1][2]. It is less common than non-small cell lung cancer, which is a different type of lung cancer that makes up about 85% of cases^[4].

Overall, about 57 in 100,000 people in the United States develop lung cancer, and small cell lung cancer represents roughly 15% of those diagnoses^[1]. The incidence of small cell lung cancer has decreased over the last four decades, reflecting decreases in smoking rates and changes to cigarettes^[4].

Types of small cell lung cancer

There are two main types of small cell lung cancer. The cancer cells of each type grow and spread in different ways. The types are named based on how the cells look when viewed under a microscope^[6]:

• Small cell carcinoma (also called oat cell cancer): This is the most common form of small cell lung cancer. It is a type of lung cancer that can grow and spread quickly, often leading to the cancer spreading to other parts of the body early in the disease process^[1][6].
• Combined small cell carcinoma: This represents about 2% to 5% of all small cell carcinomas. This type is a combination of non-small cell and small cell lung cancer cells in the same tumor^[1][6].

How small cell lung cancer affects the body

Small cell lung cancer starts when healthy cells in the lungs change into cancerous cells. These cells then divide and multiply uncontrollably. Eventually, the cancerous cells clump together in masses called tumors in the lungs^[1].

These tumors may shed cancer cells that the blood or lymph (fluid that travels through your body to your lymph nodes) pick up and carry throughout your body^[1]. Small cell lung cancer typically spreads to lymph nodes, bones, brain, liver, and adrenal glands, which are located near the kidneys^[1].

Due to how quickly it grows and spreads, in 60% of small cell lung cancer cases the cancer has already spread to other areas in the body by the time it is diagnosed^[2]. Common sites for metastasis (when cancer spreads to another part of the body) are the lymph nodes, liver, bones, adrenal glands and brain^[2].

Small cell lung cancer may also cause fluid to build up in the lungs or in the space around the lungs. It can make the lung collapse by pushing air out of the lung. This is called a pleural effusion^[1].

When small cell lung cancer spreads, it can cause symptoms that are not typically associated with lung cancer, including bone pain, seizures, confusion and paralysis^[2].

Symptoms and warning signs

Small cell lung cancer that hasn’t spread rarely causes symptoms^[1]. Nearly 25% of lung cancer cases do not produce any symptoms at all^[2]. When symptoms do happen, they may include^[1][2]:

• A cough that doesn’t go away or gets worse over time
• Coughing up blood
• Chest pain or discomfort
• Difficulty breathing or shortness of breath
• Wheezing
• Hoarseness
• Fatigue
• Loss of appetite
• Unexplained weight loss
• Facial swelling
• Swollen neck veins
• Trouble swallowing

Many of these symptoms are similar to other less serious conditions. Having one or more of these symptoms isn’t a sign you have small cell lung cancer. That said, if you smoke or you used to smoke and you notice these types of symptoms, talk to a healthcare provider. They’ll evaluate your situation and recommend any next steps^[1].

Causes and risk factors

Smoking tobacco is the leading risk factor for small cell lung cancer, responsible for 98% of all small cell lung cancer diagnoses^[2]. The more you smoke and the earlier in life you began smoking, the greater your risk for small cell lung cancer^[2]. There is a dose-dependent relationship between the degree of smoke exposure and the relative risk of lung cancer^[4].

While anyone can get lung cancer, people who smoke, used to smoke, or who are exposed to tobacco smoke (secondhand smoke) have an increased risk of developing small cell lung cancer^[1]. Other risk factors include^[1][2]:

• Exposure to secondhand smoke
• Exposure to radiation from cancer treatments or imaging scans
• Exposure to radon gas, which is a colorless radioactive gas that may seep into homes and other buildings
• Exposure to workplace hazards like asbestos, arsenic, chromium, beryllium, nickel, soot, tar or toxic chemicals
• Living in an area with air pollution
• Having a family history of lung cancer
• Having human immunodeficiency virus (HIV) infection
• Taking beta carotene supplements while being a heavy smoker
• Older age

When smoking is combined with other risk factors, the risk of lung cancer is increased^[5].

Diagnosis and testing

If lung cancer is suspected, your doctor will recommend imaging tests such as CT scans, PET scans, or MRI scans to identify abnormalities in and around your lungs^[2]. Your doctor may also take a sample of your mucus to look for cancer cells^[2].

If these initial tests identify cancer, a biopsy can be performed by either inserting a needle or making an incision in your chest to remove a small bit of tissue from your lung for further inspection^[2]. Another technique doctors commonly use to both visualize and remove lung tissue is called bronchoscopy^[2].

Your doctor will also determine the extent to which the small cell lung cancer has spread throughout your body. This descriptive process, called staging, can help inform treatment^[2]. Although numerical stages are used for small cell lung cancer as well as for other cancers, small cell lung cancer is often classified as either limited-stage (LS), where the cancer is confined to a reasonable radiation field within the chest, or extensive-stage (ES)^[2].

Treatment options

The main treatments for small cell lung cancer include chemotherapy, radiation therapy, surgery, chemoradiation (chemotherapy combined with radiation therapy), and immunotherapy^[6]. You may have one or more of these treatments depending on the stage of your cancer and how well the treatment works^[6].

Chemotherapy

Small cell lung cancer often responds well to treatment with chemotherapy. It is most commonly treated with a combination of two drugs, which is more effective than one drug alone. The most common chemotherapy drug combinations used are cisplatin and etoposide, or carboplatin and etoposide^[18].

Radiation therapy

Most people with small cell lung cancer have radiation therapy. External beam radiation therapy uses a machine to direct radiation at the lung tumor and the surrounding lymph nodes in the chest^[18]. Prophylactic cranial irradiation (PCI) is external beam radiation given to the whole brain. It may help prevent brain metastases and improve survival when small cell lung cancer has responded well to chemotherapy and radiation therapy^[18].

Chemoradiation

Chemotherapy is often combined with radiation therapy to treat limited-stage small cell lung cancer. This is called chemoradiation, where the two treatments are given during the same time period. Chemoradiation is only offered if you are healthy enough to have both treatments at the same time^[18].

Surgery

Because of the high rate of metastasis, surgery is rarely recommended for small cell lung cancer^[2]. However, in rare cases, surgery may be part of a treatment plan for limited-stage small cell lung cancer that was found as a nodule (spot) in your lung and that has not spread to the lymph nodes or outside the lung^[18].

Immunotherapy

Anti-PD-L1 or anti-PD-1 antibodies have been used along with chemotherapy in the first-line treatment of small cell lung cancer and have improved overall survival, though the benefit is not significant^[13].

It is important to see a medical oncologist and radiation oncologist as soon as possible after a diagnosis of small cell lung cancer so that treatment can be started right away^[2].

Prognosis and outlook

Small cell lung cancer patients respond to chemotherapy initially, but most acquire resistance rapidly and relapse quickly^[13]. Although there are additional therapies for relapsed patients, their response to further therapies is substantially reduced^[13].

Small cell lung cancer patients have a median progression-free survival of approximately five months and an average overall survival of 12 months^[13]. The life expectancy for a patient diagnosed with small cell lung cancer is under one year^[7].

Healthcare providers can cure some people if the disease is found early; for others, they can help them live longer^[1]. Less than 7% of patients diagnosed with extensive-stage small cell lung cancer survive five years past diagnosis^[2].

Prevention

The only way to prevent small cell lung cancer is to stop smoking^[1]. The best preventive strategy is not to smoke, and if you do, to quit as soon as possible^[2].

Reducing the frequency of smoking is one of the main prevention methods for small cell lung cancer, and the ever-decreasing incidence confirms its effectiveness^[13].