Lung Cancer

Breast Cancer | Lung Cancer | Lymphoma | Prostate Cancer

• Cigarette smoking is the most common cause of lung cancer
• One common presenting symptom is a persistent cough
• Chest x-rays can detect most lung cancers, but other additional imaging tests and biopsies are needed
• Surgery, chemotherapy, targeted agents, and radiation therapy may all sometimes be used to treat lung cancer.

Lung cancer is the leading cause of cancer death in both men and women. It occurs most commonly between the ages of 45 and 70, and has become more prevalent in women in the last few decades because more women are smoking cigarettes.

Cancer that originates from lung cells is called a primary lung cancer. Primary lung cancer can start in the airways that branch off the trachea to supply the lungs (the bronchi) or in the small air sacs of the lung (the alveoli). Cancer may also spread (metastasize) to the lung from other parts of the body (most commonly from the breasts, colon, prostate, kidneys, thyroid gland, stomach, cervix, rectum, testes, bone, or skin).

There are two main categories of lung cancer.

• Non–small cell lung carcinoma: About 85 to 87% of lung cancers are in this category. This cancer grows more slowly than small cell lung carcinoma. Nevertheless, by the time about 40% of people are diagnosed, the cancer has spread to other parts of the body outside of the chest. The most common types of non–small cell lung carcinoma are squamous cell carcinoma, adenocarcinoma, and large cell carcinoma.
• Small cell lung carcinoma: Also called oat cell carcinoma, this cancer accounts for about 13 to 15% of all lung cancers. It is very aggressive and spreads quickly. By the time that most people are diagnosed, the cancer has metastasized to other parts of the body.

Causes

Cigarette smoking is the leading cause of cancer, accounting for about 85% of all lung cancer cases. About 10% of all smokers (former or current) eventually develop lung cancer, and both the number of cigarettes smoked and number of years of smoking seem to correlate with the increased cancer risk. In people who quit smoking, the risk of developing lung cancer decreases, but former smokers will still always have a higher risk of developing lung cancer than people who never smoked.

About 15% of people who develop lung cancer have never smoked. In these people, the reason why they develop lung cancer is unknown. Recent studies have found that some people with lung cancer who have never smoked have genetic mutations in the epidermal growth factor receptor (EGFR) gene. Although an environmental association has not clearly been established, it is believed that exposure to radon gas in the home may be a risk factor. Other possible risk factors include exposure to secondhand smoke and exposure to carcinogens such as asbestos, radiation, arsenic, chromates, nickel, chloromethyl ethers, mustard gas, or coke-oven emissions, encountered or breathed in at work. It is believed that the risk of contracting lung cancer is greater in people who are exposed to these substances and who also smoke cigarettes. Air pollution and cigar smoke also contain carcinogens, and exposure to these substances is associated with an increased risk of cancer. In rare incidences, lung cancers, especially adenocarcinoma and bronchioloalveolar cell carcinoma (a type of adenocarcinoma), develop in people whose lungs have been scarred by other lung disorders, such as tuberculosis.

Symptoms

The symptoms of lung cancer depend on its type, its location, and the way it spreads. One of the more common symptoms is a persistent cough or, in people who have a chronic cough, a change in the character of the cough. Some people cough up blood or sputum streaked with blood (hemoptysis). Rarely, lung cancer grows into an underlying blood vessel and causes severe bleeding. Additional nonspecific symptoms of lung cancer include loss of appetite, weight loss, fatigue, chest pain, and weakness.

Complications

Lung cancer may cause wheezing by narrowing the airway. Blockage of an airway by a tumor may lead to the collapse of the part of the lung that the airway supplies, a condition called atelectasis. Other consequences of a blocked airway are shortness of breath and pneumonia, which may result in coughing, fever, and chest pain. If the tumor grows into the chest wall, it may produce persistent, unrelenting chest pain. Fluid containing cancerous cells can accumulate in the space between the lung and the chest wall (pleural effusions). Large amounts of fluid can lead to shortness of breath. If the cancer spreads throughout the lungs, the levels of oxygen in the blood drop and become low, causing shortness of breath and eventually enlargement of the right side of the heart and possible heart failure (cor pulmonale).

Lung cancer may grow into certain nerves in the neck, causing a droopy eyelid, small pupil, sunken eye, and reduced perspiration on one side of the face—together these symptoms are called Horner's syndrome. Cancers at the top of the lung may grow into the nerves that supply the arm, making the arm painful, numb, and weak. Tumors in this location are often called Pancoas't tumors. When the tumor grows into nerves in the center of the chest, the nerve to the voice box may become damaged, making the voice hoarse.

Lung cancer may grow into or near the esophagus, leading to difficulty swallowing or pain with swallowing.

Lung cancer may grow into the heart or in the midchest (mediastinal) region, causing abnormal heart rhythms, blockage of blood flow through the heart, or fluid in the sac surrounding the heart (pericardial sac).

The cancer may grow into or compress one of the large veins in the chest (the superior vena cava); this condition is called superior vena cava syndrome. Obstruction of the superior vena cava causes blood to back up in other veins of the upper body. The veins in the chest wall enlarge. The face, neck, and upper chest wall—including the breasts—can swell, causing pain. The condition can also produce shortness of breath, headache, distorted vision, dizziness, and drowsiness. These symptoms usually worsen when the person bends forward or lies down.

Lung cancer may also spread through the bloodstream to other parts of the body, most commonly the liver, brain, adrenal glands, spinal cord, or bones. The spread of lung cancer may occur early in the course of disease, especially with small cell lung cancer. Symptoms—such as headache, confusion, seizures, and bone pain—may develop before any lung problems become evident, making an early diagnosis more complicated.

Paraneoplastic syndromes

consist of effects that are caused by cancer but occur far from the cancer itself, such as in nerves and muscles. These syndromes are not related to the size or location of the lung cancer and do not necessarily indicate that the cancer has spread outside the chest. These syndromes are caused by substances secreted by the cancer (such as hormones, cytokines, and various other proteins).

Uncommon Lung Tumors

Lung tumors can be cancerous or noncancerous. Some less common noncancerous lung tumors include:

• Hamartomas, which are the most common noncancerous lung tumors
• Bronchial cystadenomas, which grow in the main or smaller bronchi

Rare cancerous tumors include:

• Bronchial carcinoid tumors, which may be cancerous or noncancerous
• Lymphomas, which are cancers of the lymphatic system

All lung tumors require medical evaluation because even noncancerous tumors can cause problems if they grow and block breathing. The treatment of lung tumors depends on whether they are cancerous or noncancerous. Some noncancerous tumors may need to be removed surgically to prevent the airway from becoming blocked.

Diagnosis

Doctors explore the possibility of lung cancer when a person, especially a smoker, has a persistent or worsening cough or other lung symptoms (such as shortness of breath or coughed-up sputum tinged with blood). Usually, the first test is a chest x-ray, which can detect most lung tumors, although it may miss small ones. Sometimes a shadow detected on a chest x-ray done for other reasons (such as before surgery) provides doctors with the first clue, although such a shadow is not proof of cancer.

A computed tomography (CT) scan may be done next. CT scans can show characteristic patterns that help doctors make the diagnosis. They also can show small tumors that are not visible on chest x-rays and reveal whether the lymph nodes inside the chest are enlarged. Newer techniques, such as positron emission tomography (PET) and a certain type of CT called helical (spiral) CT, are improving the ability to detect small cancers. Oncologists frequently use PET-CT scanners, which combine the PET and CT technology in one machine, to evaluate patients with suspected cancer. Magnetic resonance imaging (MRI) can also be used if the CT or PET-CT scans do not give doctors sufficient information.

A microscopic examination of lung tissue from the area that may be cancerous is usually needed to confirm the diagnosis. In rare cases, a sample of coughed-up sputum can provide enough material for an examination (called sputum cytology). Almost always, doctors need to obtain a sample of tissue directly from the tumor. One common way to obtain the tissue sample is with bronchoscopy. The person's airway is directly observed and samples of the tumor can be obtained. If the cancer is too far away from the major airways to be reached with a bronchoscope, doctors can usually obtain a specimen by inserting a needle through the skin while using CT for guidance. This procedure is called a needle biopsy. Sometimes, a specimen can only be obtained by a surgical procedure called a thoracotomy. Doctors may also perform a mediastinoscopy, in which they take and examine samples of enlarged lymph nodes (a biopsy) from the center of the chest to determine if inflammation or cancer is responsible for the enlargement.

Once cancer has been identified under the microscope, doctors usually do tests to determine whether it has spread. A PET-CT scan and head imaging (brain CT or MRI) may be done to determine if lung cancer has spread, especially to the liver, adrenal glands, or brain. If a PET-CT is not available, CT scans of the chest, abdomen, and pelvis and a bone scan are done. A bone scan may show that cancer has spread to the bones. Because small cell lung cancer can spread to the bone marrow, doctors sometimes also do a bone marrow biopsy.

Cancers are categorized on how large the tumor is, whether it has spread to nearby lymph nodes, and whether it has spread to distant organs. The different categories are used to determine the stage of the cancer. The stage of a cancer suggests the most appropriate treatment and enables doctors to estimate the person's prognosis.

Cancer Screening

Clinical trials are underway to determine the value of screening tests to detect lung cancer in people who do not have any symptoms. These trials use chest x-rays, CT scans, sputum examinations, or all these methods to try to detect cancer when it is at an early stage. However, screening so far has not been shown to improve lung cancer detection, and therefore screening is not recommended for people who have no risk factors and no symptoms. Tests can be expensive and cause people undue worry if they produce false-positive results that incorrectly imply that a cancer is present. The opposite is also true. A screening test can give a negative result when a cancer really does exist. For these reasons, it is important for doctors to try to accurately determine a person's risk for a particular cancer before screening tests are done.

Prognosis

Lung cancer has a poor prognosis. On average, people with untreated advanced non–small cell lung cancer survive 6 months. Even with treatment, people with extensive small cell lung cancer or advanced non–small cell lung cancer do especially poorly, with a 5-year lung cancer survival rate of less than 1%. Early diagnosis improves survival. People with early non–small cell lung cancer have a 5-year survival of 60 to 70%. However, people who are treated definitively for an earlier stage lung cancer and survive but continue to smoke are at high risk of developing another lung cancer.

Cancer survivors must have regular checkups, including periodic chest x-rays and CT scans to ensure that the cancer has not returned. Usually, if the cancer returns, it occurs within the first 2 years. However, frequent monitoring is recommended for 5 years after lung cancer treatment, and then people are monitored yearly for the rest of their lives.

Because many people die of lung cancer, planning for terminal care is usually necessary. Advances in end-of-life care, particularly the recognition that anxiety and pain are common in people with incurable lung cancer and that these symptoms can be relieved by appropriate drugs, have led to an increasing number of people being able to die comfortably at home, with or without hospice services.

Treatment

Individual lung cancer treatment may vary depending upon the cancer patient and their desire to receive tradition treatment, alternative cancer treatment, or integrative treatment for lung cancer.  It is vital that persons diagnosed with, or suspected of having lung cancer consult with their health care provider to assure proper evaluation, treatment and interpretation of information contained on this site.

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