Each person has two lungs: the right lung and the left lung. The lungs are surrounded by your rib cage. The right lung has three sections, or lobes: the upper, middle, and lower lobes. The right lung in general makes up about 55% of your total lung function. The left lung is smaller and has two sections, or lobes: the upper and lower. The left lung makes up about 45% of your total lung function. The primary function of the lungs is gas exchange, taking in oxygen and eliminating carbon dioxide. The pleura is a thin layer lining the lungs. The pleura protects your lungs and helps them slide back and forth against the chest wall as they expand and contract during breathing.
Below the lungs, a thin, dome-shaped muscle called the diaphragm separates the chest from the abdomen. When you breathe, the diaphragm moves up and down, forcing air in and out of the lungs.
Lung Cancer Statistics
Lung cancer is the second-most common cancer among both men and women (excluding skin cancer). Lung cancer is the leading cause of cancer death in the United States, and makes up almost 25% of all cancer deaths. Each year, more people die of lung cancer than of colon, breast, and prostate cancers combined. The American Cancer Society estimates that there will be about 228,820 new cases of lung cancer and about 135,720 deaths from lung cancer in the US in 2020. However, the number of new lung cancer cases has started to decrease over the past few years and the number of deaths have also decreased, partly because of people stopping smoking and also because of early detection and advances in treatment.
Survival in people with lung cancer varies depending on the stage of the cancer when it is diagnosed. For a person diagnosed with localized cancer (cancer has not spread outside the lung), 5-year survival is 61%. (Lung Cancer Survival Rates) Some people with early stage lung cancer can be cured with treatment.
Lung Cancer Types
Lung cancer can generally be divided into two main types: Non-small cell lung cancer (NSCLC) and Small cell lung cancer (SCLC). Non–small cell lung cancer (NSCLC) represents 80% to 90% of all lung cancer cases each year. Small cell lung cancer (SCLC) represents 10% to 20% of all lung cancer cases each year.
NSCLC has three main types: adenocarcinoma, squamous cell carcinoma, and large cell carcinoma. Adenocarcinoma is the most common type of NSCLC and starts in the cells that would normally secrete substances such as mucus. This type of lung cancer occurs mainly in current or former smokers, but it is also the most common type of lung cancer seen in non-smokers. It is more common in women than in men, and it is more likely to occur in younger people than other types of lung cancer. Adenocarcinoma is usually found in the outer parts of the lung and is more likely to be found before it has spread.
People with a type of adenocarcinoma called adenocarcinoma in situ (previously called bronchioloalveolar carcinoma) tend to have a better outlook than those with other types of lung cancer.
Squamous cell carcinomas comprise about 25% of NSCLC cases. These start in the cells that line the inside of the airways in the lungs. They are often seen in people with a history of smoking and tend to be found in the central part of the lungs, near a main airway (bronchus).
Large cell (undifferentiated) carcinoma: Large cell carcinoma can appear in any part of the lung. It tends to grow and spread quickly.
Small Cell Lung Cancer represents 10% to 20% of all lung cancer cases each year. SCLC tumors tend to grow more quickly than NSCLC tumors. About 70% of people with SCLC will have cancer that has already spread at the time they are diagnosed. These tumors may initially be more responsive to chemotherapy.
Along with the main types of lung cancer, other tumors can occur in the lungs.
Lung carcinoid tumors: Carcinoid tumors of the lung account for fewer than 5% of lung tumors. Most of these grow slowly.
Other lung tumors: Other types of lung cancer such as adenoid cystic carcinomas, lymphomas, and sarcomas, as well as benign lung tumors such as hamartomas are rare. These are treated differently from the more common lung cancers
Cancers that spread to the lungs: Cancers that start in other organs (such as the breast, pancreas, kidney, or skin) can sometimes spread (metastasize) to the lungs, but these are not lung cancers. For example, cancer that starts in the breast and spreads to the lungs is still breast cancer, not lung cancer. Treatment for metastatic cancer to the lungs is based on where it started (the primary cancer site).
Risk Factors for Lung Cancer
Smoking is the number one risk factor for lung cancer. The American Cancer Society estimates that 80% to 85% of all lung cancer cases in the United States are linked to smoking—and this includes people who have quit smoking. There is no safer form of smoking, as lung cancer has been linked to smoking cigarettes, cigars, and pipes. Smoking marijuana may also increase the risk, especially in young people. Exposure to secondhand smoke also increases the risk.
Lung cancer risk increases as you age. Only about 10% of cases occur in people younger than age 50.
Researchers are learning that certain genetic mutations are linked to lung cancer. People who have those mutated genes may be more likely to get lung cancer. Having one of these genes may be why some nonsmokers get lung cancer.
Other harmful substances can cause lung cancer, including radon and asbestos. Radon is a naturally occurring odorless, tasteless, invisible, radioactive gas. People exposed to high radon levels are more likely to get lung cancer. In fact, radon exposure is a leading cause of lung cancer in nonsmokers.
Exposure to asbestos, a mineral-based substance once used in insulation and building construction, can cause lung cancer, especially in smokers.
Symptoms of lung cancer
Early stage lung cancer is often asymptomatic, and many times it is discovered on a chest X-ray, a computed tomography (CT) scan; or a test that’s done for something else, such as for a lung infection or trauma (fall, car accident). If a lung cancer is symptomatic, the first signs are usually a persistent cough and shortness of breath. Other symptoms include: coughing up blood, chest, shoulder or back pain, voice changes (hoarseness), recurrent lung infections, difficulty swallowing.
If lung cancer has spread to other parts of the body, symptoms may also include weakness, fatigue, unintentional weight loss, bone or joint pain, headaches, memory loss, loss of balance, neck or face swelling.
Treatment of Lung Cancer
Lung cancer treatment depends on the type of lung cancer and the stage of lung cancer. Some of the most common treatments for lung cancer include:
Surgery. Surgery is the initial treatment of choice. Each lung is divided into sections, called lobes. The right lung has three lobes: upper, middle, and lower. The left lung has just two lobes: upper and lower. Surgery may be able to remove the cancer (lobectomy). In these cases, surgery has the highest cure rate. Recent advances in surgery have led to most cancer operations being done minimally invasively (either video assisted or robotic assisted), which is a safe way to remove cancer with less pain and shorter recovery.
Chemotherapy. Chemotherapy uses medications to kill cancer cells. Most chemotherapy drugs are given directly into the veins through an intravenous (IV) line. Some chemotherapy medications come in pill form (oral chemotherapy). In advanced NSCLC, chemotherapy can be used alone or with other cancer treatments.
Radiation therapy. RT uses high-energy X-rays or other forms of radiation to kill cancer cells. It can be delivered in several ways. In most cases, the patient lies on a special treatment table. A machine delivers invisible radioactive beams through the skin to the cancer.
Radiation can harm healthy tissue. The radiation oncology team will carefully measure and mark the spot to focus the radiation. During treatment, the beams will be aimed at that precise spot. Each treatment takes only a few minutes.