Small Cell Lung Cancer

Small Cell Lung Cancer

Also called: SCLC, Oat Cell Carcinoma, Small Cell Lung Carcinoma, Oat Cell Cancer

Reviewed By:
Martin E. Liebling, M.D., FACP

Summary

Lung cancer is the leading cause of cancer deaths in the United States and the world. There are two main types of lung cancer: non-small cell lung cancernon-small cell lung cancer (NSCLC), which comprises most cases of lung cancer, and small cell lung cancer (SCLC). Small cell lung cancer makes up about 13 percent of all lung cancer cases, according to the American Cancer Society (ACS). The disease occurs slightly more often in men than women. There is no significant difference in occurrence between races.

Lung cancer in general is the abnormal growth of malignant cells in the tissues of the lungs and airways. SCLC is an aggressive form of cancer that grows fast and spreads early in its development. Often it is not detected until it has metastasized (spread) to other areas of the body.

Symptoms of this form of lung cancer are the same as NSCLC and include persistent cough, blood in the sputum, breathing problems, chest pain and fatigue. To diagnose this cancer, a physician will take a medical history, perform a physical examination and order diagnostic tests such as chest x-rays, MRI, CAT scan and biopsy.

However, as with many cancers, symptoms may not appear until the disease has advanced. Because SCLC has often spread at the time of diagnosis, treatment is difficult, and SCLC has a lower survival rate as compared to NSCLC. An estimated 20 to 30 percent of people with extensive SCLC live at least one year, according to the ACS. This rate improves to 60 percent for people receiving treatment for limited-stage SCLC.

SCLC is usually treated with a combination of chemotherapy drugs and radiation therapy. Surgery is not usually recommended unless the disease remains limited to a small area of a lung. Although SCLC may be initially responsive to treatment, the disease often recurs.

Nearly all cases of small cell lung cancer are related to smoking, according to the ACS. There are no early detection methods, but quitting smoking and avoiding second-hand smoke reduce the likelihood of developing SCLC.

About small cell lung cancer

Lung cancer is the leading cause of cancer deaths in men and women throughout the world. Lung cancer is often thought of as a single disease, but it is commonly divided into two main types: non-small cell lung cancers (NSCLC) and small cell lung cancer (SCLC). Small cell lung cancer is less common than NSCLC, accounting for only about 13 percent of lung cancer cases. SCLC is also called oat cell carcinoma, because it appears like oat grains under a microscope.

Lung cancer is the abnormal growth of malignant cells in the tissues of the lungs or airways. Cancer cells develop because of damage that occurs to DNA,the genetic blueprint present in every cell. DNA governs how a cell grows, divides and dies. The body can usually repair damage to DNA. In cancer cells, however, the DNA is not repaired and the abnormal cells reproduce very quickly and often live longer than normal cells.

The lungs are sponge-like, cone-shaped organs located in the chest cavity. The left lung has three lobes and the right has two lobes. The lungs are part of the respiratory system and are responsible for the healthy exchange of gases that nourish and cleanse the body’s cells. There is a system of small (bronchioles) and larger tubes (bronchi) that carry air to and from the lungs for processing in tiny air sacs called alveoli. The oxygen is carried through the bloodstream and made available to the cells in the body. The bloodstream also picks up the waste product carbon dioxide from the cells, and transports it to the lungs to exhale.

Lung cancers can spread quickly, but SCLC is particularly aggressive. The disease is characterized by rapid division of cells (mitosis) and a high growth factor. SCLC usually begins in the bronchi, though a small percentage may begin in a peripheral area of the lung, such as the lining. It often metastasizes by way of the lymphatic system and blood vessels at an early stage.

Because it can spread so quickly, SCLC is not staged using traditional methods. Physicians use two categories to stage SCLC, according to the National Cancer Institute (NCI):

  • Limited-stage SCLC. The cancer is found in one lung, the tissues between the lungs and nearby lymph nodes only. About 30 percent of patients with SCLC will be in the limited stage, according to the NCI, with a median survival rate of 16 to 24 months. However, surgery may be possible in certain patients, which can improve the prognosis.
  • Extensive-stage SCLC. The cancer has spread outside of the lung in which it began or to distant parts of the body. The median prognosis for extensive stage is 6 to 12 months.

SCLC can be fatal within two to four months from the time of diagnosis because it typically has spread by the time it is detected. However, SCLC is more responsive initially to chemotherapy and radiation therapy as compared to other forms of lung cancer. An estimated 20 to 30 percent of people with extensive SCLC live at least one year, and this rate improves to 60 percent for people receiving treatment for limited stage SCLC.

Small cell lung cancer occurs slightly more often in men than women. There is no significant difference in occurrence between black people and white people. However, an estimated 98 percent or more of SCLC patients have a history of smoking, according to the American Cancer Society (ACS). Before the 20th century, when cigarettes were not mass produced or readily available, lung cancer in general was rarely seen. As cigarettes became widely available, cases of lung cancer rose dramatically.

The connection between cigarettes and lung cancer is overwhelming. Wherever smoking is on the increase in the world, there is a corresponding rise in lung cancer cases. Other risk factors for lung cancers include family history of lung cancer, age and exposure to certain environmental agents such as radon gas or asbestos.

The ACS estimates there will be more than 213,000 new cases of lung cancer (both NSCLC and SCLC) in 2007. The disease will be responsible for about 161,000 American deaths in the same year. The most effective means to prevent lung cancer is not smoking or quitting the habit.

Types and differences of small cell lung cancer

There are three types of small cell lung cancer (SCLC). These types are named for their appearance under a microscope and the kind of cell found in the cancer.

  • Small cell carcinoma (oat cell)
  • Mixed small cell/large cell carcinoma
  • Combined small cell carcinoma (a mix of SCLC with squamous cell or glandular cells)

Signs and symptoms of small cell lung cancer

Like non-small cell lung cancer, SCLC typically does not show symptoms until it has spread. Not all symptoms are the same in every patient. Many of the symptoms are the same as in non-small cell lung cancer, including:

  • Persistent cough
  • Coughing up blood (hemoptysis)
  • Chest pain, particularly during deep breathing
  • Wheezing
  • Shortness of breath
  • Persistent hoarseness
  • Pain or difficulty breathing or swallowing
  • Repeated infections (e.g., bronchitis, pneumonia)
  • Swelling of the face and neck
  • Weight loss
  • Loss of appetite
  • Fatigue

SCLC is also associated with a number of endocrine syndromes because the cancer cells secrete neuroendocrine hormones. When these syndromes are caused by tumors, they are called paraneoplastic syndromes and are different from those caused by NSCLC.  In some cases, the signs and symptoms of a paraneoplastic syndrome eventually lead to a diagnosis of SCLC. Signs and symptoms of paraneoplastic syndromes include the following:

  • Syndrome of inappropriate antidiuretic hormone (SIADH). A hormone that decreases urine output and dilutes blood salt levels. Symptoms of SIADH include fatigue, loss of appetite, muscle weakness or cramps, nausea, vomiting, confusion and restlessness. Untreated, SIADH can lead to seizures and coma.
  • Excessive blood clot formation. Clots most often develop in the veins of the legs, impeding blood flow. However, they may also occur in blood vessels to other limbs, the lungs, brain or other vital areas of the body.
  • Loss of balance and coordination.

Symptoms that may appear as the cancer metastasizes will reflect the area involved, and may include:  

  • Pain at metastatic sites (e.g., bones)
  • Confusion or seizures
  • Headaches
  • Double vision
  • Chest pain
  • Masses near the skin’s surface

To date, there is no screening test that has been proven to prevent people from dying of lung cancer. Scientists have studied the effectiveness of chest x-rays, certain CAT scans and cytology testing of sputum as screening tools. However, there is no conclusive evidence that these tests can find lung cancer early enough to make a difference in improving the chance of survival. For this reason, routine screening is not considered a standard practice among the general population.

Diagnosis methods for small cell lung cancer

Initially, a physician obtains a patient’s medical history, including any tobacco use, smoke exposure and family hsitory of cancer. The physician will conduct a physical examination of the patient’s body for signs of disease and other health problems.

Imaging tests, which use x-rays, magnetic fields or radioactive substances (e.g., CAT scans, MRIs, PET scans) are often used to create a picture of the body.

Other tests that may be used to diagnose SCLC include blood and urine tests, which can identify chemical or hormonal abnormalities suggestive of cancer, or sputum cytology tests. In this test, a sample of sputum or phlegm is taken for microscopic examination. At times, this test has led to early detection of carcinomas.

A biopsy sample is usually taken and viewed under a microscope to confirm a suspected diagnosis of small cell lung cancer. Samples may be obtained by a number of procedures, including bronchoscopy, mediastinoscopy, needle biopsy and others. Abiopsy can determine the type and stage of the cancer, which is used for treatment planning and prognosis.

Treatment options for small cell lung cancer

Chemotherapy is most often used with SCLC because of the rapid spread of cancer cells and because of the responsiveness of the tumor. Chemotherapy is used for both limited and extensive-stage SCLC. Radiation therapy may be used in addition to chemotherapy to help destroy or shrink tumor cells in the tumor and  lymph nodes. Surgery is rarely used to treat this type of cancer. It may be helpful if the cancer is found in only one lung and has not spread farther than the nearby lymph nodes. It is usually followed by chemotherapy and/or radiation therapy.

Other treatments for SCLC include:

  • Prophylactic cranial irradiation (PCI). A preventative treatment with radiation therapy used to reduce the chance of tumors growing in the brain. Small cell lung cancer often spreads to the brain.
  • Comfort (palliative) care. Patients have the option of receiving treatment for their symptoms without treating the cancer.
  • Clinical trials. A physician may recommend participation in a clinical trial that will test experimental treatments. Patients with small cell lung cancer are often recommended for clinical trials because of the aggressive growth of SCLC and the limitations of standard treatments. Clinical trials are conducted for all stages of small cell lung cancer. Currently, there is significant interest in experimental therapies such as biological therapy, gene therapy and angiogenesis inhibitors.

Treatment depends on the type and stage of SCLC as well as other factors, such as the age and general health of the patient. Regardless of the treatment, all lung cancer patients should quit smoking. Studies have shown that patients who continue to smoke after they have been diagnosed with lung cancer have poorer outcomes than those who stop smoking.

Ongoing research in small cell lung cancer

There are numerous agencies, organizations and medical facilities conducting research in the area of lung cancer. The basic areas of focus include:

  • Prevention. Research is focusing on ways to help people quit smoking with a variety of methods, such as nicotine replacement products and medications. Studies also are examining the role of diet, vitamins and supplements in cancer prevention.
  • Earlier diagnosis. Researchers continue to study various diagnostic methods for earlier detection of lung cancer. A large clinical trial called the National Lung Screening Trial (NLST) is studying whether  the use of spiral CT scans with people at high risk will improve diagnosis. In addition, scientists are searching for improved methods for detecting cancer cells in sputum samples to detect lung cancer at an earlier stage.
  • Chemotherapy. Research is focusing on the development of new chemotherapy drugs and drug combinations that can be effective with less toxic side effects. Studies are also being conducted to evaluate effective pairing of chemotherapy drugs with surgery and radiation therapy.
  • Gene therapy. Scientists have continued to focus on DNA and their changes that result in cancerous cells. They hope to develop ways to alter lung cancer by changing DNA or to use DNA to repair gene mutations.
  • Angiogenesis inhibitors and vaccines. Researchers hope to develop certain drugs that may be useful in stopping lung cancer growth by preventing new blood vessels from forming. Blood vessels are necessary to nourish cancer cells, a process known as angiogenesis. Without the nourishment, the cancer would not be able to grow. Antiangiogenesis drugs may be successful in stopping this nourishment process.Researchers are also examining other targeted therapies that may help prevent the growth and spread of cancer cells.

    Vaccines are also being studied in an attempt to make the body’s immune system fight cancer. Some vaccines are currently being used in clinical trials.

In August 2005, The National Cancer Institute (NCI) announced a new initiative to aggressively fight lung cancer. Using an integrated approach, its mission is to eliminate suffering and death due to lung cancer by 2015. The new plan will focus on three critical areas:

  • Reducing the risk factors for lung cancer by eliminating the use of tobacco
  • Earlier detection and treatment of lung cancer and pre-cancer
  • Targeting advanced therapies with ongoing research

As part of the plan, an Image Response Assessment Team (IRAT) will be established. The IRAT will focus on the analysis of lung cancer tumor markers and their contribution to lung cancer treatment. Researchers also intend to use advanced imaging strategies to understand lung cancer development and the response to various treatments.

Staging of small cell lung cancer

The staging of cancer is necessary for accurate treatment and prognosis of the condition. Because small cell lung cancer (SCLC) spreads so quickly, it is not staged in the traditional method. Physicians commonly use two categories to stage SCLC, according to the National Cancer Institute:

  • Limited-stage SCLC. The cancer is found in one lung, the tissues between the lungs and nearby lymph nodes only. About 30 percent of patients with SCLC will be in the limited stage, according to the NCI, with a  median survival rate of 16 to 24 months. However, surgery may be possible in certain patients, which can improve the prognosis.
  • Extensive-stage SCLC. The cancer has spread outside of the lung in which it began or to distant parts of the body. About two-thirds of the SCLC patients have extensive stage disease when the cancer is first diagnosed. The median prognosis for extensive stage is 6 to 12 months.

Small cell lung cancer is usually not found in early stages because of its aggressiveness. If SCLC is found only in the lung without lymph node involvement, the relative 5-year survival rate is about 21 percent. However, less than 10 percent of SCLC patients are in this category. After SCLC has shown signs of spreading outside of the lung, the 5-year survival rate drops to 11 percent. For patients who have extensive spread of the disease, the 5-year survival rate is only 2 percent.

Questions for your doctor about SCLC

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about small cell lung cancer (SCLC):

  1. What is the difference between SCLC and non-small cell lung cancer?
  2. What tests will I receive to diagnose SCLC?
  3. What type of biopsy will be performed?
  4. When and from whom will I receive my biopsy results?
  5. What is the type and stage of my cancer?
  6. What are my treatment options?
  7. What are the risks associated with this treatment?
  8. What is the prognosis given my type and stage of cancer?
  9. How will I know if the cancer has spread?
  10. What are the chances my cancer will return after treatment?
  11. Am I a candidate for any clinical trials?
  12. How will I be monitored after treatment?
  13. Am I at risk of developing other cancers?
  14. Since I was a smoker, should I consider lung cancer screening tests?
  15. Are my children at higher risk of developing lung cancer?
  16. Can you recommend a lung cancer support group?
Scroll to Top