Do competing causes of mortality contribute to overdiagnosis in lung cancer screening?

Overdiagnosed cancers are those that are screen-detected but never would have been symptomatic during patients' lifetimes. Indolent cancers are overdiagnosed cancers. Non-indolent cancers can be overdiagnosed when patients die of causes other than the screen-detected cancer and would have, in the absence of screening, been asymptomatic and undiagnosed at the time of death. This is termed competing cause of mortality (CCM) overdiagnosis. Deaths soon after screen detection may represent CCM overdiagnosis. We examined time from screen-detection to death among the 35 participants in the National Lung Screening Trial (NLST) low-dose computed tomography arm with screen-detected lung cancer and died of non-lung-cancer causes. Seven participants died within 6 months, and 20 died more than 24 months after diagnosis. Deaths due to non-lung cancer causes soon after screen detection were uncommon, arguing against widespread CCM overdiagnosis in the NLST. However, CCM overdiagnosis is likely more frequent in community-based screening given the higher prevalence of comorbidities.
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