Causes

• Cigarette smoking accounts for 85 to 90 percent of all lung cancers. Harmful substances in tobacco, called carcinogens, damage the cells in the lungs. Over time the damaged cells may become cancerous. Your risk increases with the number of cigarettes you smoke each day, the number of years you have smoked, the earlier the age at which you started smoking, and the more deeply you inhale.
• Secondhand smoke can also cause lung cancer. Daily exposure to other people’s smoke may increase your chances of developing lung cancer by as much as 30 percent.
• Radon is an invisible, odorless, tasteless radioactive gas that occurs naturally in soil and rocks. It can cause damage to the lungs that may lead to lung cancer. People who work in mines may be exposed to radon. In some parts of the country, radon is found in houses.
• Asbestos is the name of a group of minerals that occur naturally as fibers and are used in certain industries, including shipbuilding, insulation, and brake repair. Asbestos fibers break easily into particles that can be inhaled and damage the lungs. Workers exposed to large amounts of asbestos have a higher risk of developing lung cancer than people who are not exposed to asbestos. The risk is even higher among asbestos workers who smoke.
• Other causes of lung cancer include cigar and pipe smoking, lung diseases such as tuberculosis, and possibly air pollution.

Symptoms

Because the lungs are so large, cancer can invade and grow in them for many years without being detected. Cancer can even spread outside the lungs without any noticeable symptoms.

The most common warning sign of lung cancer is a persistent cough. You may also have chest, back, or shoulder pain. Other symptoms include:

• Shortness of breath
• Wheezing
• Fatigue
• Repeated cases of pneumonia or bronchitis
• Coughing up blood
• Hoarseness
• Swelling of the neck and face

If a tumor is pressing on the nerves in the lung, you may have pain and weakness in your arm, shoulder, and hand.

If you have symptoms of lung cancer, your doctor will evaluate your medical history and perform a physical exam. You may have a chest x-ray examination. To confirm the presence of lung cancer, a tissue sample must be taken from your lungs, called a biopsy. If the diagnosis is lung cancer, your doctor will do more tests to determine the stage of the cancer.

Types of Lung Cancer

Lung cancer is usually divided into two types: non–small cell carcinoma and small cell carcinoma. The terms non–small and small refer to the size of the cells, not the size of the cancer growth.

Non–small cell carcinoma is more common than small cell carcinoma, and it generally grows and spreads more slowly. There are three types of non–small cell carcinoma:

• Squamous cell carcinoma. Also called epidermoid carcinoma, it forms in the cells lining your airways. It usually does not spread as rapidly as other types of cancer.
• Adenocarcinoma. This type of cancer usually begins near the outside surface of the lung and under the lining of the breathing tubes (bronchi). This is the most common type of lung cancer among people who do not smoke.
• Large cell carcinoma. This type of cancer starts growing along the outer edges of the lung. Because the tumor grows rapidly, it is usually large by the time it is found.

Small cell carcinoma accounts for about 25 percent of all cases of lung cancer. It usually starts in one of the breathing tubes and grows more rapidly and is more likely to spread to other organs than other types of lung cancer.

Treatment

Treatment for lung cancer depends on the type of cancer (small cell or non–small cell); the size, location, and extent of the tumor; and the general health of the patient. There are several different kinds of treatment, which may be used alone or in combination:

• Surgery to remove the tumor is the most common treatment for non–small cell lung cancer. Removal of a small section of the lung containing the tumor is called wedge resection. When an entire lobe is removed (your right lung has three lobes and your left lung has two), the procedure is called a lobectomy. This is the most common type of lung cancer surgery. Pneumonectomy is the removal of an entire lung.
• Chemotherapy is the use of anticancer medications to kill cancer cells throughout the body. This is the most common treatment for small cell lung cancer and can also be used to treat non–small cell cancers. Chemotherapy may be used to control cancer growth or to relieve symptoms. It is usually given by intravenous (IV) injection into a vein or through a thin tube placed into a vein (catheter). Some anticancer medications come in the form of a pill.
• Radiation therapy kills cancer cells by exposing them to high doses of x-rays. It is directed to a limited area, and affects the cancer cells only in that area. Radiation therapy may be used before surgery to shrink a tumor or after surgery to destroy any remaining cancer cells. Doctors also use radiation therapy, often combined with chemotherapy, as the primary treatment instead of surgery.

Prevention

The most important thing you can do to reduce your risk of lung cancer is to avoid smoking and being around other people’s smoke. Even people who have smoked heavily for many years can significantly reduce their risk of lung cancer by quitting smoking.

Avoid radon and asbestos by paying attention to warnings in your buildings and worksites and by following the safety rules that are in place where you work. If you are exposed to asbestos at work, wear protective equipment. If you would like to test your home for radon, you can purchase a home radon test kit, available at most hardware stores.