December 9, 2013 | by Nicole White
Cancer screening always carries risks and benefits – usually trading a degree of “overdiagnoses” for finding cancers at early stages, when they are least lethal and most treatable.
From mammography to PSA testing, what to screen, how to screen and when to screen remains a source of debate and discussion among the medical community. A study in today’s JAMA Internal Medicine stokes debate about lung cancer screening. The study out of Duke University finds that as many as 18 percent of lung cancers found by the low-dose CT scans suggested by the U.S. Preventive Services Task Force for screening may lead to “overdiagnosis” because the cancers are slow-growing or clinically insignificant.
Dan Raz, M.D., co-director of the Lung Cancer and Thoracic Oncology Program at City of Hope, is skeptical of the findings, saying that the study should not deter patients or the medical community from proceeding with screening if a person meets the guidelines.
“Lung cancer is by far the most common cause of cancer death among men and women in the U.S. and worldwide,” he said. “One of the reasons for this is that lung cancer is aggressive, and by the time a person experiences symptoms, it is often no longer curable.”
The new study examined data from the National Lung Screening Trial, which analyzed low-dose CT screening with chest radiography among 53,452 people at high risk for lung cancer. The authors estimated that among the 1,089 lung cancers reported in the CT scan group, 18.5 percent represented overdiagnosis. They also estimated that 22.5 percent of nonsmall cell lung cancer detected by the scans represented overdiagnosis, and that 78.9 percent of cancers found in the air sacs were overdiagnosed. The authors called for better imaging and the discovery of better biomarkers to make mass screening more valuable.
Raz, however, put the study's findings in perspective. The National Lung Cancer Screening Trial and other lung cancer screening trials have conclusively shown that lung cancer screening with low-dose CT scanning potentially saves lives, is safe and is cost-effective, he said. Raz also pointed out that the observation that screening will detect slower-growing cancers is not unexpected in a screening study. Furthermore, he said, he’s skeptical of how the new study interpreted data from the National Lung Cancer Screening Trial to suggest a large portion of lung cancers detected might never have gone on to harm patients and are “unnecessarily treated.” “In fact, we know that this is not true,” he said. “A large study of patients in the California Cancer Registry with small lung cancers who refused treatment revealed the vast majority of these patients died of lung cancer. Lung cancer screening has the potential to significantly reduce suffering and death from lung cancer.”