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CT Lung Cancer Screening

Issues to Consider Before Having a CT Scan to Screen for Lung Cancer

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Updated September 20, 2012

Lung cancer screening is an area that could make a big difference in the future of lung cancer. As Pap smears have decreased the risk of cervical cancer, and colonoscopies have resulted in a decline in deaths from colon cancer, it would be wonderful to have a screening tool to detect lung cancer in the earlier, more curable stages. At this time, too many lung cancers go undetected until they are at an advanced stage. Due to late detection, the overall survival rate for individuals newly diagnosed with lung cancer is a saddening 15%.

In the past, both chest x-rays and sputum cytology were evaluated as methods to detect lung cancer at an earlier stage, but neither of these procedures were found to improve long-term survival. Hence, routine chest x-rays are no longer used in smokers to screen for lung cancer.

The only procedure currently available for lung cancer screening before symptoms are present, is a spiral (also called helical) CT scan. A spiral CT scan is similar to a conventional CT scan (the kind of CT scan most of us are familiar with) but is performed more quickly and results in less exposure to radiation. A recent large study found that high risk individuals who underwent annual CT screening for 3 years had a 20% reduced risk of dying from lung cancer. High risk in this study was defined as people between the ages of 55 and 74 who had at least a 30 pack-year history of smoking. Despite this exciting news about a lower mortality rate, other issues need to be considered in order to make a decision on whether the benefits will outweigh any potential harm. Issues to consider include:

Errors

For a screening technique to be adopted, it needs to be both sensitive, that is accurate in detecting disease in the early stages, but also specific, meaning it does not pick up too many insignificant findings. One problem with CT scans is that they can pick up spots in the lungs that are not cancerous. This can lead to unnecessary procedures to help diagnose the findings, and unnecessary surgeries. In one older study, 3 times as many lung cancers were found as predicted, but 10 times more surgeries were performed, and screening was not found to lower mortality. The recent National Lung Cancer Screening trial did show a lower risk of dying from lung cancer in high risk individuals as noted above. Yet 40% of those who were screened were found to have abnormalities on screening that later turned out to be benign. In this case the risk of false-positives (such as further radiological studies and possible biopsies) need to be weighed against the benefit of detecting a lung cancer in the earlier stages.

Exposure to Radiation

While spiral CT screening for lung cancer results in less radiation exposure than conventional CT scans (the kind of CT Scans most of us are familiar with), the risk of developing lung cancer from radiation exposure can be significant, especially if scans are done yearly. In one study, a 5.5% increase in lung cancer risk was caused by yearly screening. This means that to justify screening, it would need to increase survival by more than 5.5%. There may also be an increase in breast cancer rates in women since radiation is directed at the chest.

The Cost

Another determinant in evaluating a screening test is whether it is cost-effective. This involves looking at the cost of screening versus the effect of screening (the number of years of life saved.) It is not known clearly at this time if the cost of screening, including the workup of false positive results, can be justified as are screening methods for other cancers.

Is CT Lung Cancer Screening Right for Me?

Lung cancer screening remains an individual decision that should be discussed with your healthcare provider, who can assist you in weighing the risks and benefits of the procedure. In most cases, screening is an out-of-pocket expense that is not covered by health insurance carriers. By far the most important step is to quit smoking. Smoking causes many medical conditions in addition to lung cancer.

Sources:

American Cancer Society. Study: CT Scans Still Not Advised for Lung Cancer Screening. 03/07/07. http://www.cancer.org/cancer/news/news/study-ct-scans-still-not-advised-for-lung-cancer-screening

Bach, P. Computed tomography screening and lung cancer outcomes. Journal of the American Medical Association. 2007. 297(9):953-61.

Bach, P. Lung Cancer Screening. Journal of the National Comprehensive Cancer Network. 2008. 6(3):271-5.

Bach, P. et al. Screening for Lung Cancer. ACCP Evidence-Based Clinical Practice Guidelines (2nd Edition). Chest. 2007. 132:69S-77.

Black, W. Computed tomography screening for lung cancer: review of screening principles and update on current status. Cancer. 2007. 110(11):2370-84.

Brenner, D. Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer. Radiology. 2004. 231(2):440-5.

Henschke, C. et al. Survival of patients with stage 1 lung cancer detected by CT screening. New England Journal of Medicine. 2006. 355(17):1763-71.

McMahon, P. et al. Estimating Long-term Effectiveness of Lung Cancer Screening in the Mayo CT Screening Study. Radiology. 2008, May 5 (Epub ahead of time).

Midthun, D. and J. Jett. Update on Screening for Lung Cancer. Seminars in Respiratory and Critical Care Medicine. 2008. 29(3):233-40.

National Cancer Institute. National Lung Cancer Screening Trial. http://www.cancer.gov/NLST.

The National Lung Cancer Screening Trial Research Team. Reduced Lung-Cancer Mortality with Low-Dose Computed Tomographic Screening. The New England Journal of Medicine. 2011. 365:395-409.

Oken, M. et al. Screening by chest radiograph and lung cancer mortality: the Prostate, Lung, Colorectal, and Ovarian (PLC) randomized trial. Journal of the American Medical Association. 2011. 306(17):1865-73.

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