Screening for Lung Cancer

In the United States, lung cancer accounts for 27% of all cancer related deaths; it is estimated that 6% of babies born here this year will die of this disease. Unfortunately, if we wait until symptoms from lung cancer are manifest, there is a 75% chance that the cancer is already incurable.  For decades there has been active research into potential ways to screen for lung cancer so as to allow for earlier diagnosis-akin to mammography for breast cancer and colonoscopy for colon cancer. In 2004, the United States Preventive Services Task Force (USPSTF) issued a report on the use of chest radiography or CT scanning as a screening technology. At the time they found the evidence insufficient to support population based screening.

Since 2004 there has been further research in the area of CT screening due to its increased sensitivity compared with plain X-ray studies.  Because 85% of lung cancer patients are smokers/former smokers, the focus has been on screening in this high risk group. In the September 13, 2013 issue of the Annals of Internal Medicine (ann int med 2013; 159:411-420) the USPSTF reported that, in the light of new data, there is now strong evidence that CT scanning of SPECIFIC HIGH RISK patients can reduce death rates from lung cancer in smokers and former smokers, albeit with certain associated risks.  One significant weakness in the data is that the studies lacked representative numbers of women and minorities and, therefore, leaves some uncertainty in what to recommend certain groups.

To give a perspective on the utility of screening, the USPTF reported that 320 patients would need to be screened to prevent one lung cancer death. This compares favorably with the number of patients who need to be screened for breast cancer or colon cancer to prevent one death (1,339 and 17, respectively).

Are there downsides to screening?-potentially yes. As with any other radiation modality, CT scanning exposes healthy tissue to radiation and, with multiple exposures over years to decades, radiation induced cancer is a theoretical concern. This risk has been lessened by the use of “low dose” CT (LDCT) scanning in lung cancer screening programs.  In addition, some patients without cancer will have “false positive” scans, leading to a potential series of follow up tests.