INTRODUCTION

Lung cancer is a serious health problem that affects many people and their families. Lung cancer is the leading cause of cancer death in the United States. It is usually caused by cigarette smoke, but there are other factors in the family and in the home or workplace that can increase the risk of lung cancer.

When a person develops lung cancer, tests are done to determine the type of lung cancer and if it has spread. When a cancer spreads, this is called metastasis. The size and spread of cancer are combined into a scale that is called the cancer stage. The stage is an important feature used to help decide what treatments can be used.  

This article will review the risks for developing lung cancer and the different types of lung cancer. Next, this article will discuss the signs and symptoms of lung cancer and the medical testing required to confirm the diagnosis. Finally, this article will review the process of determining the cancer’s size and location for staging.

The treatment of lung cancer is discussed separately.

• (See "Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)".)
• (See "Patient information: Non-small cell lung cancer treatment; stage IV cancer (Beyond the Basics)".)
• (See "Patient information: Small cell lung cancer treatment (Beyond the Basics)".)

More detailed information about lung cancer is available by subscription. (See 'Professional level information' below.)

RISKS FOR LUNG CANCER

Smoking — Cigarette smoking is the biggest risk factor for lung cancer. As an example, smoking is estimated to cause 85 percent of all lung cancers in the United States. A smoker's risk of developing lung cancer is 10 to 30 times greater than that of a nonsmoker. All forms of tobacco and smoking, including pipes, cigars, and chewing tobacco, are major risk factors for cancers of the mouth, throat, and lungs. The risk of lung cancer increases with the number of cigarettes smoked and the number of years of smoking.

The risk of cancer remains high for several years after quitting smoking but the risk does go down within 5 to 10 years after quitting. A former smoker's risk of lung cancer is never as low as a nonsmoker's risk.

Environmental factors — Substances at work or in the environment can increase a person's risk of developing lung cancer. In parts of the world where fuel such as wood or coal are widely used for cooking and heating, these may be important contributors to the risk of lung cancer. Other important factors include secondhand tobacco smoke, asbestos, arsenic, radiation, and some chemicals. Dust and fumes from nickel, chromium, and other metals may also increase the risk of lung cancer.

Another important risk factor for lung cancer is radon in the home. Radon is a radioactive gas that occurs naturally in the ground. Radon can leak out of the ground and then become trapped in houses or buildings mainly in the basement, where it is then inhaled. You cannot see or smell radon, which is why testing for radon is often recommended (see www.epa.gov/radon/pubs/citguide.html).

Age and genetic risk factors — The risk of developing lung cancer increases with age. Lung cancer can occur in young people, although it is unusual in people younger than 40 years old. After age 40, the risk for developing lung cancer slowly increases every year.

Some people have a genetic risk or predisposition for lung cancer. Anyone with a first-degree relative (parent, brother, sister) with lung cancer has a higher risk of developing lung cancer themselves.

SCREENING FOR LUNG CANCER

The most important factor in reducing the risks from lung cancer is to avoid smoking. For those individuals who are at increased risk of lung cancer because of smoking, screening with low dose computed tomography may be recommended. (See "Patient information: Lung cancer prevention and screening (Beyond the Basics)".)

LUNG CANCER SYMPTOMS

Most people with lung cancer have one or more symptoms. However, the symptoms of lung cancer are similar to the symptoms of other more common problems. If you are concerned about your symptoms, talk to your doctor or nurse.

The most common symptoms of lung cancer include:

• Cough — Lung cancer can cause a new cough or a change in a chronic cough. The cough can be a dry or may produce sputum (phlegm), which can contain blood. (See "Patient information: Chronic cough in adults (Beyond the Basics)".)
• Shortness of breath
• Wheezing, a whistling sound when you breathe
• Chest pain can develop and may be dull, sharp, or stabbing
• Voice hoarseness
• Headache and swelling of the face, arms, or neck
• Arm, shoulder, and neck pain can be caused by a tumor in the top of the lungs (called a Pancoast tumor). Other symptoms can include weakening of the hand muscles (due to pressure on the nerve that stimulates the arm), a droopy eyelid, and blurred vision.

INITIAL TESTING AND DIAGNOSIS

If you have symptoms that suggest lung cancer, your doctor or nurse will perform an examination. If your findings are still concerning, more tests including blood work and x-rays or scans will then be ordered.  

If the chest X-ray or scans show an abnormal growth that could be a tumor, additional testing is performed to make a diagnosis. Usually, a piece of the growth will need to be removed and examined under a microscope. This procedure is called a biopsy.  

A biopsy can be done in one of several ways:

• Bronchoscopy is a procedure where a flexible tube with a camera is inserted under sedation through your mouth or nose and then into the windpipe (called the trachea). This procedure is described in detail separately. (See "Patient information: Flexible bronchoscopy (Beyond the Basics)".)
• CT-guided fine needle biopsy is performed by locating the tumor with a CT scan and inserting a thin needle through the skin, into the lung, to remove a tiny sample of tissue.
• Needle aspiration is performed by inserting a needle into lumps or lymph nodes that can be felt under the skin or into fluid collections in the chest.
• Surgery may be needed to remove the tumor if the tumor is small and it is not possible to get a sample of tissue any other way.

TYPES OF LUNG CANCER

There are many different kinds of lung cancer. However, there are two main categories:

• Small cell lung cancer is found in about 10 to 15 percent of patients.
• Non-small cell lung cancer (often abbreviated NSCLC) includes other types of lung cancer and is found in the remaining 85 to 90 percent of patients. There are subcategories of NSCLC, the most common of which are adenocarcinoma, squamous cell carcinoma, and large cell carcinoma.

The reason that small cell cancer is separated from non-small cell cancers is that small cell cancers behave differently and are treated differently than non-small cell cancers. Small cell cancer tends to be more aggressive and can spread quickly.

STAGING NON-SMALL CELL LUNG CANCER

Once lung cancer is diagnosed, the next step is to review its size, to determine its exact location and to find out if it has spread. This process is called staging. Determining the stage of a lung cancer can be complicated because many features of the tumor are used at the same time. The stage of non-small cell cancer is based on:

• The size and location of the tumor
• Whether the tumor has invaded lymph nodes and tissues inside the chest

• Whether the tumor has spread to places outside the chest (for example lung cancer can spread (metastasize) to places like the lymph nodes or adrenal glands or elsewhere)

Non-small cell lung cancer stages range from I to IV. In general, the lower number (stages I and II) suggest that the tumor is smaller and has not spread far. In comparison, the higher numbers (stage III and IV) suggest that the tumor is larger or has metastasized.  

• Stage I — The tumor is smaller than or equal to 5 cm in maximum diameter and has not spread to any other tissues or lymph nodes (figure 1). (See "Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)".)
• Stage II —Stage II means that the tumor is either between 3 and 7 cm in size, or it has spread to the lymph nodes, or it has invaded the tissues surrounding the lung, or it has started to invade the large bronchial tubes (figure 2). (See "Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)".)  
• Stage IIIA — Stage IIIA disease means that the tumor can be bigger than 7 cm, or has spread to the lymph nodes in the center of the chest (called the mediastinum) or has spread to the rib cage, heart, swallowing tube (called the esophagus) or to the trachea (figure 3).
• Stage IIIB – Stage IIIB disease means that the tumor has spread to lymph nodes on the other side of the mediastinum or to the lymph nodes above or behind the clavicle (collar bone). Stage IIIB also includes large tumors that have spread to the rib cage, heart, swallowing tube (called the esophagus) or to the trachea when there is involvement of the mediastinal lymph nodes (figure 4).  
• Stage IV — Stage IV means that the cancer has spread outside of the chest or has spread to a critical location or has caused some complication. Possible complications are that the cancer has caused fluid to collect around the lung or heart (called a malignant effusion), or it has spread to the opposite side of the chest, has spread to outside the chest (figure 5). (See "Patient information: Non-small cell lung cancer treatment; stage IV cancer (Beyond the Basics)".)

In general, lower-stage cancers require different kinds of treatment than do higher-stage cancers. Treatment options for early stages may include surgery to remove the cancer entirely while later stage cancers may also be treated with medications (chemotherapy) or radiation. Some higher stage tumors have spread beyond the point where cure is possible and treatment for these may include medications to treat pain and discomfort.

STAGING SMALL CELL LUNG CANCER

Technical staging for small cell cancer is exactly the same as for non-small cell cancer. However, treatment options are usually determined by a much more simple system. This is because SCLC has different growth patterns and a different prognosis. SCLC is categorized more commonly as either "limited" or "extensive" disease. This system helps to determine which treatment will be most effective.

• Limited disease — This refers to small cell lung cancers that are confined to one side of the chest and lymph nodes.
• Extensive disease — This refers to small cell lung cancer that has spread to the opposite side of the chest or has metastasized (spread) to distant locations outside the chest.

The treatment and prognosis of SCLC depends upon whether disease is limited or extensive. This is discussed in detail in a separate topic review. (See "Patient information: Small cell lung cancer treatment (Beyond the Basics)".)

CLINICAL TRIALS

Progress in treating lung cancer requires better treatments. A clinical trial is a carefully controlled way to study the effectiveness of new treatments or new combinations of known therapies. Clinical trials are conducted around the world. Ask for more information about clinical trials, or read about clinical trials at:

• http://clinicaltrials.gov/

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient information: Lung cancer (The Basics)
Patient information: Non-small cell lung cancer (The Basics)
Patient information: Small cell lung cancer (The Basics)
Patient information: Lung cancer screening (The Basics)
Patient information: Asbestos exposure (The Basics)
Patient information: Multiple pulmonary nodules (The Basics)
Patient information: Single pulmonary nodule (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient information: Non-small cell lung cancer treatment; stage I to III cancer (Beyond the Basics)
Patient information: Non-small cell lung cancer treatment; stage IV cancer (Beyond the Basics)
Patient information: Small cell lung cancer treatment (Beyond the Basics)
Patient information: Chronic cough in adults (Beyond the Basics)
Patient information: Flexible bronchoscopy (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Overview of the risk factors, pathology, and clinical manifestations of lung cancer
Cigarette smoking and other risk factors for lung cancer
Screening for lung cancer
Overview of the initial evaluation, treatment and prognosis of lung cancer
Pathology of lung malignancies
Pathobiology and staging of small cell carcinoma of the lung
Role of imaging in the staging of non-small cell lung cancer
Preoperative evaluation for lung resection
Management of stage I and stage II non-small cell lung cancer
Management of stage III non-small cell lung cancer
Overview of the treatment of advanced non-small cell lung cancer
Personalized, genotype-directed therapy for advanced non-small cell lung cancer
First-line chemotherapy for patients with extensive stage small cell lung cancer

The following organizations also provide reliable health information.

• National Cancer Institute

     (www.cancer.gov/cancertopics/types/lung)

• American Society of Clinical Oncology

     (www.cancer.net/patient/Cancer+Types/Lung+Cancer) [1-6]