Friday, October 12, 2007

Lung cancer prevention and screening

INTRODUCTION — Lung cancer is the leading cause of cancer death in both men and women in the United States. The number of people dying from lung cancer each year has risen over the past 25 years. It is estimated that lung cancer will be responsible for approximately 160,000 deaths in the US during 2006. This is more than the estimated deaths from breast cancer, prostate cancer, and colorectal cancer combined. Several factors increase the risk of lung cancer, particularly cigarette smoking.

PREVENTING LUNG CANCER — Cigarette smoking is responsible for almost 90 percent of cases of lung cancer. Exposure to certain substances, such as asbestos, has also been linked to the development of lung cancer. Exposure to second-hand smoke and other environmental factors may play a role.

The best way to avoid getting lung cancer is not to smoke. Some smokers believe that once they have smoked for a long while, it does little good to quit. However, studies have shown that smokers who quit decrease their risk of lung cancer when compared to those who continue to smoke. Smokers who quit for more than 15 years have an 80 to 90 percent reduction in their risk of lung cancer compared to people who continue to smoke. (See "Patient information: Smoking cessation").

IS SCREENING WORTHWHILE? — Screening is a way to detect a disease in its earliest stages, before a person becomes ill or dies. To be recommended, it must be clear that screening is useful in identifying patients who have the disease in the early stages, and that this discovery can reduce the number of patients who become ill and/or die.

Some screening exams have proven to make a clear difference in patient outcomes. Examples are the Pap smear for detection of cervical cancer in women, and colonoscopy for detection of colon or rectal cancer in people over 50 years old. These exams are now part of routine health care in the United States.

SCREENING EXAMS FOR LUNG CANCER — Research studies have been done to determine if screening for lung cancer makes sense. In these studies, smokers (who are at highest risk to develop the disease) are divided into groups. Some groups have screening tests while others have no screening. The groups are then followed over many years. Data are gathered on how many patients in each group are diagnosed with lung cancer, how the cancer was treated, and how long patients with lung cancer survived after treatment.

So far, the data from these studies have not shown that screening for lung cancer makes a difference in deaths from the disease. For this reason, major medical advisory groups do not yet recommend lung cancer screening.

Still, the data from these studies are the subject of much debate in the medical community. Part of the debate surrounds the fact that outcomes other than overall mortality, such as the stage of the disease at diagnosis or five-year survival rate, seem to be favorably affected by screening. However, critics point out that data are difficult to interpret reliably. The debate is continuing, and more studies are underway to better understand the role of screening studies for lung cancer

Because of the lack of data on the efficacy of screening for lung cancer, most of these exams are not part of routine care and are only offered to smokers as part of ongoing clinical trials. One exception may be the annual chest x-ray.

Chest x-ray — Many doctors already recommend an annual chest x-ray for their patients who smoke. Some experts, in analyzing data from lung cancer screening trials, have concluded that an annual chest x-ray is a worthwhile screening exam for patients with lung cancer.

Two major studies have been done to find out whether more frequent chest x-rays are beneficial in lung cancer screening. So far, these studies have not shown a clear benefit in terms of deaths from lung cancer. In patients who had more frequent chest x-rays, more lung cancers at early stages were found, the cancers were more frequently removable by surgery, and the patients had longer five-year survival (from time of diagnosis) than patients with less frequent x-rays. However, overall mortality from lung cancer was not significantly affected.

Computed tomography (CT scan) — Studies of computed tomography (CT scan) of the lung have shown that the test can help detect early stage lung cancer, but it is not yet clear whether this will affect the number of patients who die from their cancer.

Sputum tests — Some studies have looked at the efficacy of analyzing a patient's sputum for evidence of cancer cells in order to detect lung cancer. So far, no clear benefit to this approach has been found. Additional studies that use new technologies to examine the sputum are underway.

PET scan — Researchers are looking at a number of other tools in an effort to help identify patients with lung cancer. Positron Emission Tomography (or PET scanning, which uses a small amount of radioactivity to provide a detailed picture of an organ's function) has been used in combination with CT scanning.

Other studies — Direct visualization of the lungs with bronchoscopy and breath analysis for cancer markers are two tests that may be used in future studies.

CLINICAL TRIALS — Because the data on lung cancer screening are inconclusive, large-scale clinical trials of various screening modalities are underway. Smokers or former smokers may be asked to participate in these trials.

Although it makes sense to think that early detection of lung cancer is a good idea, it is important to understand that routine screening for lung cancer cannot be recommended until the research clearly shows that it makes a difference. It is likely that recommendations on lung cancer screening will evolve over the next decades as these data become available.

SUMMARY Patients who smoke are at increased risk of developing lung cancer. The best way to avoid lung cancer is not to smoke. Even long-term smokers can benefit from quitting. Researchers are looking for ways to help smokers and non-smokers who develop lung cancer to live longer. Early detection and screening is a major focus of this effort It is not clear if lung cancer screening can reduce the number of people who die from their disease. Clinical trials are underway that will help provide answers to these questions.

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site ( Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. National Cancer Institute

People Living With Cancer: The official patient information

website of the American Society of Clinical Oncology
The American Cancer Society

Lung Cancer Alliance



Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Jemal, A, Siegel, R, Ward, E, et al. Cancer statistics, 2006. CA Cancer J Clin 2007; 57:43.
2. Truong, MT, Munden, RF. Lung cancer screening. Curr Oncol Rep 2003; 5:309.
3. Nawa, T, Nakagawa, T, Kusano, S, et al. Lung cancer screening using low-dose spiral CT: results of baseline and 1-year follow-up studies. Chest 2002; 122:15.
4. Bastarrika, G, Garcia-Velloso, MJ, Lozano, MD, et al. Early Lung Cancer Detection using Spiral Computed Tomography and Positron Emission Tomography. Am J Respir Crit Care Med 2005; 171:1378.

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