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Lung Cancer
Overview
According to the American Cancer Society, an estimated 221,130 new cases of lung cancer will be diagnosed in 2011, making lung cancer the second most common type of cancer in both men and women in the United States. The rate of new cases (known as incidence) of lung cancer varies according to gender and race/ethnicity. Across all races/ethnicities, the incidence is higher among men than women, and the highest rates are found for black and white men.
How Lung Cancer Develops
Lung cancer is the uncontrolled growth of abnormal cells in the tissues of the lung, usually in the cells lining the bronchi (airways) (Figure 1). Researchers believe that lung cancer develops slowly over the course of many years after exposure to cancer-causing substances (carcinogens). The overwhelming cause of lung cancer is tobacco products, such as cigarettes, pipes or cigars. The earlier in life a person starts smoking, the more packs of cigarettes a person smokes, and the more years a person smokes, the greater the risk for lung cancer. Once a person stops smoking, the risk becomes lower each year, but the risk is still higher than for people who have never smoked. However, people who never smoked may also get lung cancer. Spending a great deal of time in places where other people are smoking exposes you to secondhand smoke. Exposure to asbestos or radon, family history, and race/ethnicity are other risk factors.
Even though lung cancer grows slowly, it spreads through the blood at any early time and it is difficult to detect lung cancer early primarily because of two reasons. First, there are no early symptoms of lung cancer and many of the first symptoms, such as cough, are also symptoms of chronic lung disease caused by tobacco products. The lack of symptoms means that there is nothing to alert a person to seek medical care. Second, there are no established tests for early detection, as there are for other major types of cancer, such as colorectal, breast and cervical cancers. Thus, lung cancer is usually not detected until it is at a later stage.
Although there is currently no reliable screening method for lung cancer, effective screening may be on the horizon. A large study, the National Lung Screening trial, recently showed that using low-dose spiral computerized tomography (CT), also known as helical CT, to screen high-risk individuals (defined as people who were 55-74 years old and had smoked the equivalent of a pack of cigarettes daily for 30 or more years) led to 20% fewer lung cancer deaths compared with screening with standard chest x-rays. However, a large number of patients had small nodules that were not cancer. Individuals who are at high risk of lung cancer should discuss a screening spiral CT scan with their doctor. More studies are needed for other high-risk individuals to determine the cost-effectiveness of helical CT screening, to evaluate ways to limit radiation exposure, and to determine the optimal evaluation of positive scans, most of which do not represent cancer. Research is also needed to identify reliable markers in blood, sputum, and urine that indicate the presence of lung cancer.
Figure 1
The lungs are spongy, air-filled organs located on either side of the chest (thorax). The right lung has three lobes, and the left lung has two lobes. Air enters the lungs through the nose and mouth, moving through the windpipe (trachea) and into the airways (bronchi) in the lung. These airways divide into smaller branches, called bronchioles, and end in microscopic air sacs (alveoli), where oxygen and carbon dioxide are exchanged.
The lungs are covered by a thin layer of tissue called the visceral pleura. Another layer of this same kind of tissue lines the inside of the chest cavity; this layer is called the parietal pleura. Fluid between these two tissue layers acts as a lubricant as the lungs expand and contract during breathing. The diaphragm is a muscle at the base of the lungs that helps in breathing.
Source of figure: the website of the National Cancer Institute: www.cancer.gov.
Types of Lung Cancer
There are four main histologic (pathologic) types of lung cancer: small cell carcinoma, large cell carcinoma, adenocarcinoma, and squamous cell carcinoma (see Table 1). The histologic type is determined by the pathologist who looks at a sample of tumor tissue under a microscope. Small cell lung cancer most often spreads to other sites and may grow much faster than the other types. Thus, small cell carcinoma was sometimes distinguished from the three other types, which were classified together as “non-small lung cancer.” This distinction is no longer relevant because each histologic type may be treated differently and may have different driver mutations, or genetic alterations that drive the growth of the cancer. Since the identification of these genetic alterations, the type of lung cancer is becoming further defined by the presence or absence of specific mutations.
The most common histology is adenocarcinoma, followed by squamous cell carcinoma, small cell carcinoma, and large cell carcinoma. All histologic types are caused by cigarette smoking, but adenocarcinoma is the histologic type that most often occurs in people who have never smoked.
Table 1. Classification of Lung Cancer
|
Type |
Frequency (Among All Lung Cancers) |
Where It's Usually Found |
Other Features |
|
Non-small cell (NSCLC) |
80-85% |
|
The exact type of NSCLC must now be distinguished for optimal therapy. |
|
Adenocarcinoma |
35-40% |
Glands of the lungs that produce mucus; often in the outer edges of the lung |
Most common type of lung cancer overall, in women, and in people who have never smoked. Type for which the most driver mutations have been identified. |
|
Squamous cell carcinoma |
25-30% |
Lining of the bronchial tubes; usually in the center parts of the lung |
Highly associated with tobacco smoking. |
|
Large cell carcinoma |
10-15% |
Can occur anywhere in the lung but usually near the surface, at the outer edges of the lung |
Grows more quickly than the other two subtypes. |
|
Small cell (SCLC) |
15-20% |
In the center of the lung, with invasion of the hilar and medistinal areas and disease in nearby lymph nodes |
The cancer cells multiple rapidly and form large tumors that can spread throughout the body; current and former smoking is almost always the cause. |
Five Things You Should Know About Lung Cancer
1. NOT ALL LUNG CANCERS ARE THE SAME.
As with many other types of cancer, lung cancer is not just one disease. Instead, there are different types of lung cancer, classified according to the specific tissue in the lung in which they develop. Determining the classification of lung cancer and the stage of disease is important, because treatment is selected according to histology and stage. Learn about the diagnosis and staging of lung cancer.
2. YOU DON’T HAVE TO SMOKE TO GET LUNG CANCER.
Although the overwhelming cause of lung cancer is smoking, not all people with lung cancer are smokers. In fact, the most common type of non-small cell lung cancer (adenocarcinoma) occurs most often in people who have never smoked. You may not have to smoke to get lung cancer, but if you do smoke, you have to quit! Quitting is not easy, and it may take several attempts before you’re successful, but you can get help from several resources. Ask your doctor how he or she can help you quit.
3. LUNG CANCER TREATMENT IS GETTING PERSONAL.
As researchers discover more information about how lung cancer develops, they are finding genetic alterations that can be targets for newer types of drugs. These genetic alterations are leading the way for personalized treatment of lung cancer, with treatment selected according to the specific characteristics of an individual tumor.
4. SIDE EFFECTS OF TREATMENT CAN BE ALLEVIATED.
Treatments for lung cancer may cause side effects, but there are now many ways to manage side effects. Talk to your doctors about the potential side effects of your treatment options and ask if there are ways to prevent these side effects. During treatment, tell your doctor or other member of your health care team about symptoms you have so that they can be managed before they become severe.
5. YOU CAN TAKE CONTROL.
A diagnosis of lung cancer is overwhelming, and it is easy to feel as if your life is out of control. But you have the power to overcome many challenges of lung cancer. Don’t be afraid to ask your doctor about treatment options and to state your preferences. Take good care of yourself by getting proper nutrition, exercise, and sleep. Do whatever it takes to help you heal and feel physically and emotionally healthy, whether it be mediation, yoga, relaxation techniques, spirituality, or counseling. Spend time with family and friends and be specific about what you need — and don’t need — from them. Enjoy your favorite activities. Live every day to its fullest.
This Content
This content is primarily for men and women who have had a suspicious mass detected on an imaging study or have had lung cancer diagnosed. In the pages that follow, you will find information on how doctors diagnose and stage lung cancer and work within a multidisciplinary team to plan treatment designed to achieve the best outcomes possible for your particular lung cancer tumor. You will also learn about the various treatment options, the potential side effects of treatment and their management, the management of lung cancer symptoms related to metastasis, and how to take control of your life after a lung cancer diagnosis. Throughout, you will be directed to websites where you can find more details to help you better understand lung cancer and its treatment.
Additional Sources of Information
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