Am Fam Physician. 2008 Sep 15;78(6):764-767.
Background: Lung cancer is expected to claim the lives of more than 160,000 Americans in 2007. Early surgical resection can be curative, but it generally has a poor prognosis because symptoms rarely present in the early stages. Sputum cytology and chest radiography have been previously investigated as screening tools, but with disappointing results. Multiple studies have shown that these screening tools may detect more early-stage cancers and lead to higher rates of surgery, but do not decrease the incidence of advanced lung cancer or reduce mortality. Previous reviews of lung cancer screening are in nearly complete agreement that lung cancer screening with chest radiography or sputum cytology is inappropriate. However, several new technologies have emerged that could have potential benefits as screening tools, namely low-dose computed tomography (CT), biomolecular markers (e.g., the evaluation of exhaled breath for lung cancer-associated DNA alterations) and proteomics (detecting blood and tissue genetic alterations).
The Study: This study updated previous lung cancer screening guidelines by the American College of Chest Physicians (ACCP), focusing only on recent developments and newer studies of lung cancer screening. The authors conducted a systematic literature review from 2002 to 2005 of studies examining lung cancer screening or the clinical behavior of lung cancers identified through screening. Recommendations were developed using a standardized method and were approved by the Thoracic Oncology Network, Health and Science Policy Committee, and the Board of Regents of the ACCP.
Results: Low-dose CT is the most promising of current lung cancer screening techniques. It is about three times more sensitive than chest radiography at detecting small lung nodules that will be diagnosed as cancer, but analyses of projected tumor-doubling times and clinical detection rates have suggested that most of these tumors are actually indolent and are unlikely to affect the mortality from faster-growing tumors that are more likely to be clinically significant. Neither low-dose CT nor chest radiography has been shown to reduce the number of late-stage lung cancers or the risk of dying from lung cancer. One recent study examining 1,520 current and former smokers who received annual low-dose CT screening found no reduction in lung cancer mortality, which mirrored the results of other studies of screening with chest radiography. Several large randomized trials examining low-dose CT are ongoing, but results are not expected until at least 2009.
Determining an appropriate “high-risk” population for screening has also been difficult. Even for smokers, the estimated cost-effectiveness is daunting; for example, one study that hypothetically assumed that low-dose CT screening could reduce lung cancer mortality by 13 percent over 20 years still resulted in a cost of $2,322,700 per quality-adjusted life-year gained in former smokers.
Biomolecular markers and proteomics have shown promise in detecting early lung cancers; however, both techniques are still in their infancy and require formalized effectiveness and cost-effectiveness analyses before being considered as screening methods.
Conclusion: The current recommendations against routine screening for lung cancer using serial chest radiography or sputum cytology remain unchanged. Although the introduction of low-dose CT scanning shows promise for detecting small tumors, it is not recommended for screening in patients with no history of lung cancer, except in the context of a well-designed clinical trial. The use of biomolecular markers requires further clinical evaluation before formal recommendations can be made about their use.
Bach PB, et al. Screening for lung cancer: ACCP evidence-based clinical practice guidelines (2nd edition). Chest. September 2007;132(3):69S–77S.
Copyright © 2008 by the American Academy of Family Physicians.
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