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Overdiagnosis, Extended Follow-up of Mayo Lung Project

Overdiagnosis is detecting disease that would never have been diagnosed without screening. The Mayo Lung Project was a large randomized controlled trial of lung cancer screening among male cigarette smokers in the 1970s and early 1980s. Its results indicated that overdiagnosis of lung cancer was associated with screening. At the end of follow-up in 1983, the screened and usual care arms did not differ in lung cancer mortality, but more cases were found in the screened arm than the usual-care arm. Because these extra cases could have been due to short follow-up, Marcus et al. (p. 748 ) extended the follow-up by 16 years. They found that 585 lung cancers were diagnosed in the screened arm and 500 in the usual-care arm. They conclude that the persistent excess lung cancers in the intervention arm even after extended follow-up supports overdiagnosis associated with lung cancer screening.