A cancer that begins in the lungs is known as lung cancer. It occurs when the cells in the lungs mutate and grow abnormally to form a mass of cells; these cells may or may not spread to the other parts of the body.
Lung cancer is the most common cancer and the leading cause of cancer death worldwide. In 2018, about 2.1 million lung cancer cases were estimated globally with 1.8 million deaths.
Types of lung cancer
Based on how the cells appear under the microscope, lung cancer is divided into the following types:
Small cell lung cancer (SCLC): SCLC is an aggressive cancer that accounts for 10-15% of all lung cancers. It is usually observed in heavy smokers and about 70% of cancers are at the advanced stages when diagnosed.
Non-small cell lung cancer (NSCLC): NSCLC is more common than SCLC, which accounts for about 80-85% of all lung cancers. NSCLC is sub-divided into squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
Signs and symptoms
The symptoms of lung cancer may vary among individuals. Typically, they are not apparent during the earlier stages of the cancer and may appear only during the advanced stage.
The signs and symptoms of lung cancer may include:
- Persistent cough that may get worsen
- Coughing up blood
- Chest pain
- Shortness of breath
- Loss of appetite
- Unexplained weight loss
Causes and Risk factors
The exact cause of lung cancer is unknown. However, it is evident that these risk factors increase the chance of developing lung cancer.
- Second-hand smoke exposure
- Radon gas exposure
- Family history of lung cancer
- History of radiation therapy to chest
- Exposure to Asbestos, arsenic, chromium, and some forms of silica
Chronic smokers, people aged above 55 years, and people who have a high risk of lung cancer must undergo yearly screening. Some lung cancers can be identified by screening, but majority of them are only found when they start causing problems.
Following are the diagnostic tests that may be recommended to check for the presence of cancer or to rule out other conditions.
Medical history and physical examination: Details related to possible risk factors and symptoms are obtained. Physical examination is performed and involves identification of possible signs for the presence of other health problems.
When lung cancer is suspected, more detailed tests are recommended and may include:
Chest X-ray: It is a primary imaging test recommended to reveal any abnormal areas in the lungs.
Sputum cytology: A sputum sample is collected and checked for the presence of lung cancer cells under the microscope. Samples are often collected early in the morning for at least three consecutive days to obtain reliable results.
Biopsy: A biopsy involves obtaining a sample of abnormal tissue from the affected area and observing it under the microscope to find any abnormalities. It can be performed in many ways depending on the location of the tumor.
- Bronchoscopy: During bronchoscopy, a lighted tube is passed through the throat into the lungs to look for abnormalities, such as tumors or blockages in the larger airways of the lungs, which can be biopsied during the procedure.
- Mediastinoscopy: During mediastinoscopy, a lighted tube is inserted through an incision made at the base of the neck into the space in the chest between the lungs, called mediastinum. Tissue samples can be taken from the lymph nodes along the windpipe or the bronchi.
- Fine needle aspiration (FNA): A procedure known as transtracheal FNA or transbronchial fine FNA can be performed during which a fine needle is passed through the wall of trachea or bronchi to withdraw abnormal cells.
- Transthoracic needle biopsy: During this procedure, an X-ray or CT scan is used to guide a needle through the chest wall into the lung tissue to obtain the cells for examination.
The cells obtained are sent for laboratory analysis that can provide information about the type of lung cancer. Extensive analysis also helps to determine specific characteristics of the cancer cells, thereby helping in the treatment plan.
Imaging tests are done to identify the presence of cancer and to check for the extent of cancer spread to other parts of the body (cancer staging).
- Computer Tomography (CT): A CT scan can help detect tumors that may remain unnoticed in routine chest X-rays. It provides information related to the size, shape, and position of the lung tumors. It may also help to look if the cancer has spread to other parts of the body, such as liver or adrenal glands.
- Magnetic resonance imaging (MRI): An MRI can reveal the size, location and extent of a lung tumor.
- Positron emission tomography (PET) scan: A PET scan uses a radioactive substance (tracer) to look for abnormalities in the lung tissues. Often it is combined with a CT scan to help differentiate between cancerous and noncancerous tumors.
Stages of lung cancer
Staging of lung cancer plays a key role in treatment planning and also helps to know the prognosis of the lung cancer.
- Stage 0: The tumor is confined to top layer of cells lining the lungs and not spread into deeper tissues of the lungs.
- Stage I: Cancer has invaded into lung tissues but not spread to nearby lymph nodes.
- Stage II: The cancer may have spread to nearby lymph nodes.
- Stage III: The cancer has spread into the lymph nodes in space between the lungs.
- Stage IV: The cancer has spread to distant lymph nodes or organs, such as brain, bones or liver.
The treatment for lung cancer depends on a number of factors such as the type and extent of lung cancer, the patient’s general health and his treatment preferences.
Surgery involves removal of the tumor along with the margin of the surrounding healthy tissue. The surgery requires general anesthesia and is performed by making large incision in the chest wall between the ribs. This procedure is known as thoracotomy.
Types of surgery for lung cancer:
- Pneumonectomy: Involves removal of the whole lung
- Lobectomy: Involves removal of the entire lobe containing the tumor
- Segmentectomy (wedge resection): Involves removal of a part of the lobe
- Segmental resection: Involves removal of a slightly larger portion of the lung, but not an entire lobe
During surgery, the lymph nodes may also be removed from the chest to check if the cancer has spread to areas other than the lungs.
Radiation therapy uses high-energy beams to destroy the cancer cells. It can be used before the surgery to shrink the tumor or after the surgery to destroy the cancer cells, which may have been left behind. The radiation therapy is often combined with chemotherapy in advanced stage lung cancer or if surgery is not an option.
Stereotactic radiotherapy (SRT) is a type of radiation therapy that involves administering radiotherapy from many different angles around the body. People with small lung cancers who are not candidates for surgery can be treated with SRT. It may also be used to treat lung cancer that has spread to other parts of the body, including the brain.
Chemotherapy involves using anti-cancer drugs that are given either intravenously or orally to kill cancer cells. It is either used alone or in combination with the radiation therapy. It can be used prior to the surgery to shrink the tumor or after the surgery to destroy the cancer cells that could be left behind. It may also help to relieve symptoms such as pain during advanced lung cancer.
Targeted drug therapy
Targeted drug treatments focus on specific changes within the cancer cells that help them grow, divide and spread. The featured advantage of targeted therapy is that it helps to specifically target the cancerous cells, thereby minimizing the damage of normal cells.
Immunotherapy triggers the immune system to control or eliminate cancer. It is often recommended for patients with locally advanced cancers and cancers that have spread to other parts of the body.
Lung cancer cannot be prevented, however evidences suggest that the risk of lung cancer may be decreased by:
- Smoking cessation
- Avoiding secondhand smoke
- Avoiding exposure to carcinogens
- Being physically active
- Consuming fruits and vegetables
- Consuming foods rich in retinol, beta-carotene or carotenoids, vitamin C (current smokers)
The survival rates vary depending on the extent of cancer spread at the time of diagnosis. An early diagnosis significantly improves the outcomes with timely therapeutic intervention. However, as lung cancer does not usually cause noticeable symptoms until advanced stages, the outlook for the condition is poor compared to other cancer types. About one in three people with this condition live for at least one year after they are diagnosed and about one in 20 people live for at least ten years.
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