Lung cancer is a malignancy that originates in the tissues of the lungs. There are two main types: small cell lung cancer and non-small cell lung cancer. Both are characterized by a very rapid and uncontrolled growth of cells. Accounting for approximately 15 to 20% of all lung cancer cases, small cell lung cancer is less common—and more aggressive—than non-small cell lung cancer. Because small cell lung cancer cells exhibit features of nerve cells and hormone-secreting (endocrine) cells, this type of lung cancer is characterized as a neuroendocrine carcinoma.
Types of small cell lung cancer
In general, small cell lung cancer can be categorized as one of two types:
- Limited-stage small cell lung cancer — The cancer is confined to one side of the chest. In addition to the lung in which it originated, cancer may be found in the area between the lungs or in the lymph nodes above the collarbone.
- Extensive-stage small cell lung cancer — The cancer has spread beyond the side of the chest in which it originated to distant tissues and organs.
If small cell lung cancer comes back after it is treated, it is known as recurrent small cell lung cancer. The cancer may recur in the chest, the central nervous system or another part of the body.
How is small cell lung cancer diagnosed?
If small cell lung cancer is suspected based on a patient’s symptoms, a diagnosis may be confirmed after a thorough clinical evaluation and a variety of specialized tests. The diagnostic process often begins with a chest X-ray, which may reveal a mass in a lung. If a mass is identified, a physician may order a more specialized imaging test—such as a computed tomography (CT) scan, a positron emission tomography (PET) scan, a magnetic resonance imaging (MRI) scan or a bone scan—to determine whether a tumor is present and, if so, the extent and spread of the cancer.
The next step in the diagnostic process is to determine the specific type of cancer present. To do so, a physician will typically order a biopsy, which involves obtaining a small sample of the tumor so that a pathologist can determine its cellular makeup by analyzing the tissue under a microscope. In order to obtain the tumor sample, the physician may recommend a bronchoscopy or a fine needle aspiration. During a bronchoscopy, a physician inserts a bronchoscope through the patient’s mouth and into the affected lung to remove tissue. During a fine needle aspiration, a physician inserts a thin, hollow needle into the tumor. The needle is attached to a syringe, which the physician uses to draw out a small sample of tissue and fluid from the tumor.
A physician may also order a mediastinoscopy to determine whether the cancer has spread to the lymph nodes in the middle of the chest. After making a small incision near the top of the breastbone, a surgeon passes a small, thin tube with a camera attached (mediastinoscope) behind the breastbone and along the windpipe in order to view and obtain tissue samples from the mediastinum, which is the area between the lungs in the central region of the chest.
What causes small cell lung cancer?
The predominant cause of small cell lung cancer is exposure to certain carcinogenic chemicals found in tobacco smoke. In fact, the vast majority of affected individuals are current or former heavy smokers or have a history of chronic exposure to secondhand smoke.
While scientists have established that the carcinogens found in tobacco smoke can directly damage cellular DNA, it is still unclear how the damaged DNA leads to the development of cancer. Current research suggests that multiple genetic and environmental factors may be at play. For instance, certain genetic changes acquired during life, such as through exposure to tobacco smoke, may affect the oncogenes and tumor suppressor genes that normally regulate cell growth. An altered oncogene or tumor suppressor may promote very rapid and uncontrolled cell growth, leading to the development of cancer.
What are the symptoms of small cell lung cancer?
The signs of small cell lung cancer can vary widely based on numerous factors, such as the location and size of the tumor and whether the cancer has invaded nearby tissues or spread to distant areas of the body. In its early stages, small cell lung cancer is often completely asymptomatic or produces only very mild symptoms, such as coughing. Typically, additional symptoms become apparent as the cancer progresses.
In many cases, the first noticeable sign of small cell lung cancer is a persistent cough, which may be accompanied by:
- Chest pain that worsens with deep breathing, coughing or laughing
- Shortness of breath
- Coughing up blood
- Vocal hoarseness
- Difficulty swallowing
- Loss of appetite
- Unintended weight loss
- Unexplained fatigue
- Facial swelling
- Recurrent episodes of lung infections, such as pneumonia or bronchitis
The symptoms of metastatic small cell lung cancer can vary based on the specific areas of the body affected. The most frequently affected tissues and organs are the:
- Lymph nodes — Possible symptoms include small, painless lumps and skin growths
- Brain — Possible symptoms include headaches, dizziness, double vision, seizures and tingling sensations in the arms, hands, legs or feet
- Liver — Possible symptoms include yellowing of the eyes and skin (jaundice)
- Bones and bone marrow — Possible symptoms include bone pain
Some individuals with small cell lung cancer also develop paraneoplastic syndromes, which can result from an abnormal immune system response to a cancerous tumor. Researchers believe that white blood cells, which normally protect the body against viruses, bacteria and other foreign invaders, may inadvertently attack healthy tissues and cause a variety of neurological issues, such as numbness, weakness and confusion.
Paraneoplastic syndromes can also develop due to the excessive hormone production that often accompanies small cell lung cancer. One example is the syndrome of inappropriate antidiuretic hormone secretion, which is characterized by excessive production of a hormone that reduces urination. This can lead to water retention and low sodium levels and ultimately cause fatigue, lethargy and confusion.
How is small cell lung cancer treated?
The specific therapies used to address small cell lung cancer can vary based on a number of factors, including the size and stage of the tumor and the extent of its spread, as well as the patient’s age, overall health and symptoms.
Treatment options for limited-stage small cell lung cancer
If the cancer is confined to one small lung tumor, its surgical removal may be considered. Usually, surgery is followed by a course of chemotherapy. In general, this treatment approach is appropriate only if the cancer has not spread beyond the lung in which it originated. Because small cell lung cancer typically progresses very rapidly, the tumor has usually spread at least to the nearby lymph nodes or other areas of the chest by the time it is diagnosed.
More often, limited-stage small cell lung cancer is treated with concurrent chemoradiation, which involves the simultaneous administration of chemotherapy and radiation therapy. If this relatively aggressive treatment approach is ruled out due to a patient’s health, chemotherapy may be administered first, followed by radiation therapy to the chest.
Treatment options for extensive-stage small cell lung cancer
If the cancer has spread throughout the body, surgery and radiation therapy will generally be of limited benefit. Instead, the cancer may be treated with chemotherapy. Then, if the cancer responds well to chemotherapy, treatment may continue with radiation therapy to the chest.
Moffitt’s multispecialty approach
Firmly positioned at the forefront of lung cancer treatment, Moffitt Cancer Center is proud to offer the very latest surgical procedures, chemotherapy regimens and radiation delivery techniques, along with a robust portfolio of clinical trials. At Moffitt, each patient receives a thorough evaluation and a highly individualized treatment plan based on his or her specific needs. The multispecialty team in our Thoracic Oncology Program includes thoracic surgeons, medical oncologists, radiation oncologists and supportive care specialists who focus exclusively on lung cancer treatment.