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. While several studies have found these effective in detecting lung cancers at an earlier stage, you have to consider other issues. For a procedure to be adopted as an effective screening tool, it has to not only pick up disease at an early stage, but improve long-term survival and quality of life as well. The benefits of early detection need to outweigh any potential harm. Issues to consider include:
Errors in CT Lung Cancer Screening
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 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.Exposure to Radiation From CT Lung Cancer Screening
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 of CT Lung Cancer Screening
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.Who recommends CT Lung Cancer Screening?
According to the the American College of Chest Physicians (AACP) guidelines for lung cancer screening, screening is only recommended for individuals that are part of a well-designed clinical trial. The American Cancer Society does not advise routine lung cancer screening at this time.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.
When Will We Know More About CT Lung Cancer Screening?
It is hopeful that the controversy over CT screening for lung cancer will be clarified in the next few years. The National Cancer Institute is currently conducting a study of 50,000 smokers and former smokers who are randomized to have spiral CT screening for lung cancer yearly for 3 years. The study is expected to be completed in late 2009, but results may be available earlier if screening is shown to save lives.Sources:
American Cancer Society. Study: CT Scans Still Not Advised for Lung Cancer Screening. http://www.cancer.org/docroot/NWS/content/NWS_1_1x_Study_CT_Scans_Still_Not_Advised_for_Lung_Cancer_Screening.asp. 03/06/07.
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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).
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National Cancer Institute. National Lung Cancer Screening Trial. http://www.cancer.gov/NLST.
