The results of pilot trials comparing low-dose computerized tomography (LDCT) with chest radiographs in high-risk patients have shown that screening with LDCT decreases the mortality rate from lung cancer and can increase the diagnosis of early stage lung cancer (Aberle DR, et al. N Engl J Med. 2011;365:395-409; Henschke CI, et al. N Engl J Med. 2006;355:1763-1771) . Based on these results the National Comprehensive Cancer Network (NCCN) recommends screening with LDCT for select high-risk current and former smokers. New data, however, suggest that use of LDCT may result in overdiagnosis and detection of clinically insignificant tumors. These results should be considered carefully as lung-cancer screening programs are developed.
More than 18% of all lung cancers detected by low-dose computed tomography (LDCT) appeared to represent an overdiagnosis, according to a study published in JAMA Internal Medicine.
Overdiagnosis is the detection of a cancer with a screening test that wouldn’t otherwise have become clinically apparent. It is a potential harm of screening because of the additional cost, anxiety, and complications associated with unnecessary treatment, according to the study background.
In recent clinical trials, LDCT has been shown to be an effective screening tool in some patients that has demonstrated a 20% relative reduction in lung cancer-specific mortality compared with chest radiography (CXR). However, some of the tumors detected by LDCT may be slow growing or even clinically insignificant.
To estimate overdiagnosis, a team of researchers examined data from the National Lung Screening Trial, which compared LDCT screening versus CXR among 53,452 people at high risk for lung cancer.
Among 1089 lung cancers reported in the LDCT group during follow-up, the authors estimated that 18.5% represented an overdiagnosis. They also estimated that 22.5% of non-small cell lung cancer detected by LDCT represented an overdiagnosis, and that 78.9% of bronchioalveolar lung cancers detected by LDCT represented an overdiagnosis.
These data suggest that while LDCT may be associated with a relative mortality reduction, the limitations of the screening process, including misdiagnosis, must be considered as screening programs are designed. The authors conclude that “In the future, once there are better biomarkers and imaging techniques to predict which individuals with a diagnosis of lung cancer will have more or less aggressive disease, treatment options can be optimized, and a mass screening program can become more valuable.”
- Patz W, Pinaky P, Gatsonis C, et al. Overdiagnosis in low-dose computed tomography screening for lung cancer. JAMA Intern Med. 2013. Epub ahead of print. December 9, 2013. Full text available at: http://archinte.jamanetwork.com/article.aspx?articleid=1785197#Abstract. Accessed December 11, 2013.