Small Cell Lung Cancer: Overview and More

Small cell lung cancer (SCLC) accounts for about 15% of all lung cancers. It can cause symptoms ranging from fatigue to coughing up blood and is more aggressive than the more common non-small cell lung cancer (NSCLC) . Smoking is the leading cause of SCLC and a biopsy is needed to confirm the diagnosis. Although it may initially respond to radiation and chemotherapy, SCLC can spread rapidly, often making surgery or final treatment less viable.

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Symptoms of small cell lung cancer

This type of cancer usually doesn't cause any noticeable problems at first. But once symptoms appear, they can quickly get worse over the course of a few weeks .

The first symptoms of small cell lung cancer can result from lung damage, such as shortness of breath. But the first symptoms of SCLC can be systemic (including general metabolism or bodily functions), such as weight loss.

The effects of the SCLC may include:

As the tumor grows, it can invade structures near the lungs, such as the chest, esophagus, and throat, with symptoms.

Signs of metastasis

If SCLC metastasizes (spreads) to other parts of the body, its systemic manifestations are more likely than when it is limited to the lungs. Metastatic SCLC can also cause fate-related problems in the body, sometimes without causing any lung-related symptoms.

The effects of metastatic SCLC can include:

Paraneoplastic effects

SCLC can also cause paraneoplastic syndromes . These conditions occur when cancer cells produce hormones that travel through the bloodstream and stimulate other organs or cells, usually in harmful ways.

Although these paraneoplastic effects are rare, they are more common in SCLC than other types of lung cancer and can be the first noticeable signs of the disease.

The paraneoplastic effects of SCLC can include :

  • Paraneoplastic cerebellar degeneration: loss of coordination, erratic eye movements, and problems with voice control.
  • Lambert-Eaton myasthenic syndrome: weakness and fatigue of the arms, changes in vision and difficulty swallowing.
  • Polyneuropathy : decreased muscle sensitivity and / or weakness throughout the body.
  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH): weakness, fatigue and low levels of sodium in the blood.
  • Paraneoplastic limbic encephalitis , which causes personality changes and memory impairment .


SCLC is closely related to smoking, although it is also related to other risk factors, such as exposure to radon and asbestos. The incidence of SCLC is declining in the United States and a decrease in the number of smokers is believed to be a possible explanation for this .

SCLC usually begins in the large bronchi (airways) of the lungs. This type of lung cancer begins to develop when a mutation (genetic change) causes lung cells to behave abnormally and aggressively.

SCLC rarely develops in people who have never smoked, so genetic mutations are believed to be the result of DNA damage caused by toxins in cigarette smoke .

Mutations that lead to this type of cancer have been found in the bronchial epithelium (mucous membrane) of people with SCLC. Genetic changes cause problems, including:

  • Decreased immune function.
  • Proliferation of cancer cell growth.
  • Cancer cells' propensity to spread to other areas of the body.


Genes associated with cancer include oncogenes and tumor suppressor genes .

Oncogenes are genes that are initially healthy but, if changed, can lead to cancer. Tumor suppressor genes are healthy genes that prevent cancer, but they stop working properly when they are changed by mutations.

Changes in these two types of genes are more significant in SCLC than in other types of lung cancer, and people with this cancer may have more than one type of gene mutation .

Examples of genetic mutations associated with SCLC include the RB1 and TP53 tumor suppressor genes .


The diagnosis of SCLC involves a number of approaches, including non-invasive imaging, bronchoscopy , and biopsy.

Some of the distinctive features of SCLC can be determined by imaging tests such as chest x-rays, computed tomography (CT) , magnetic resonance imaging (MRI) , ultrasound, and positron emission tomography (PET scan) . But these characteristics are not reliable enough to definitively distinguish SCLC from other types of lung cancer, or even cancer that has metastasized to the lungs from other parts of the body .

Imaging studies other than the lungs are often needed to determine if SCLC metastases are present.


The most accurate way to confirm that the cancer is NCLC is with a lung biopsy sample obtained with a bronchoscope, needle, or surgery. During the bronchoscopy procedure, a flexible device with a camera is inserted into the nose or mouth and moved down the throat to the bronchial tubes in the lungs.

Using a bronchoscope, your doctor will examine your airways and take a small sample of the tumor so that it can be thoroughly analyzed.

If a tumor biopsy cannot be done with bronchoscopy (for example, because it is out of reach), your doctor may obtain a biopsy sample with a needle inserted through the chest wall or with a more extensive surgical procedure. These invasive techniques are usually accompanied by images in order to identify the correct area.

After obtaining a tissue sample, the diagnosis of cancer is made by examining its microscopic appearance. SCLC has a distinctive appearance with small and relatively irregular lung cells that are not aligned like healthy lung cells.


Traditionally, SCLC has been classified according to the Veterans Administration Pulmonary Study Group (VALG) staging system as limited or extensive stage SCLC.

About 60% to 70% of people with SCLC already have advanced disease at the time of diagnosis .

In addition, SCLC is also classified according to the staging system used for NSCLC, which is known as the tumor node metastasis (TNM) staging system .

It uses a classification structure based on tumor size, degree of lymph node involvement, and degree of metastasis.

The TNM configuration is more descriptive. For each of the three factors, numerical values from 0 (mildest) to 4 (most severe) are used, as well as subcategories, indicated by letters .

Watch out

Treatments for SCLC include a combination of chemotherapy, radiation therapy, and surgery. If you have this type of cancer, your treatment plan will be tailored to the severity of your tumor, as well as your general health, including your ability to resist and your willingness to treat.

Treatment for SCLC can prolong survival, but is generally ineffective in treating the disease. SCLC usually recurs after initial treatment and can become resistant to subsequent chemotherapy .


Chemotherapy is one of the treatments used for SCLC, especially for lymph node involvement or metastases. This method uses powerful drugs to kill cancer cells. However, chemotherapy can be intense and cause side effects such as hair loss and nausea.

Several chemotherapy drugs are approved for the treatment of SCLC, including Mustargen (mechlorethamine hydrochloride) and methotrexate .


Immunotherapy is a type of chemotherapy that helps change the body's immune system to fight disease. Unlike traditional types of chemotherapy, immunotherapy generally does not cause widespread systemic side effects, but rather specifically targets a specific type of cancer.

Tecentrik (atezolizumab), Opdivo (nivolumab) , and Keytruda (pembrolizumab) are types of immunotherapy used to treat SCLC. Sometimes immunotherapy is used in combination with other types of chemotherapy, especially for recurrent cancer.

Radiation therapy

For both limited and advanced cancers, radiation therapy is often used in conjunction with chemotherapy and / or surgery. Radiation therapy uses powerful X-rays to kill cancer cells and can prolong life.

However, it can cause side effects, including a weakened immune system and fatigue. It also increases your risk of developing other cancers in the future.

Prophylactic cranial radiation (PCI) , prophylactic radiation therapy to the brain, is sometimes recommended to reduce the risk of brain metastases, a very common site of cancer recurrence. Side effects can include cognitive changes such as decreased memory and concentration.


Surgery is not a common treatment for SCLC because this type of cancer is often metastatic at the time of diagnosis. However, surgery is sometimes considered for a very early limited stage of cancer, when there is a small isolated nodule in the lung.

Radiation may be considered before surgery to reduce swelling and after surgery to prevent recurrence. Adjuvant chemotherapy (chemotherapy after surgery) is generally recommended if surgery is being done for small cell lung cancer.

Surgery may be recommended even for advanced disease, when it can help reduce your symptoms and improve your quality of life, for example, by removing metastases blocking the intestines.

Palliative care

In addition to treatment for SCLC, you may also need palliative care – treatment to relieve your symptoms.

For example, you may need medicine to reduce nausea, a common side effect of chemotherapy. You may also need pain relievers if you have bone metastases.

Palliative care may also include interventions such as oxygen supplementation if you find it difficult to breathe. And if you have anemia (low red blood cell count) due to a problem like coughing up blood, you may need a blood transfusion.

If you have any unpleasant symptoms of your disease, do not hesitate to seek treatment, as palliative care can improve your quality of life at any stage of cancer treatment. Your palliative cancer treatment may change throughout your illness.


Generally, the smaller and less common the SCLC, the higher the expected survival rate. Older age, lower performance , and paraneoplastic effects are also associated with a worse overall prognosis .

Immunohistochemistry is a technique in which biochemical markers are identified by chemically treating biopsy samples. Several markers are associated with a favorable or unfavorable prognosis or with an expected response to treatment. However, these approaches are still under development .

Get the word of drug information

Finding out that you have SCLC can be overwhelming, especially since this type of cancer is often recognized when it is quite advanced. Because SCLC may not respond well to standard treatment, you may want to speak with your doctor about participating in a clinical trial . You may also find it helpful to contact a support team . And don't hesitate to seek help from your healthcare team, family, or friends as you embark on your treatment plan.

Discussion Guide for Lung Cancer Doctors

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