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Lung-cancer screening leads to overdiagnosis among nonsmoking Asian women

JAMA Internal Medicine
Reuters Health - 18/01/2022 - Expanding low-dose computed tomography (LDCT) screening for lung cancer to nonsmoking populations will likely lead to overdiagnosis of lung cancer, a study from Taiwan indicates. 

"Unless randomized trials can demonstrate some value to low-risk groups, LDCT screening should remain targeted only to heavy smokers," researchers write in JAMA Internal Medicine. 

"As smoking continues to decline in many developed countries, the proportion of lung cancers in nonsmokers will rise. This shift may create substantial pressure to further expand lung cancer screening to lower-risk groups," they explain. 

They wondered what would happen to lung-cancer incidence when screening is promoted to a population of Asian women with a smoking prevalence of less than 5% since 1980. 

In their population-based, ecological cohort study of roughly 12 million Taiwanese women, they found that promoting lung-cancer screening was associated with a six-fold increase in the incidence of early-stage (stages 0-I) lung cancer from 2004 to 2018, whereas there was no change in the incidence of late-stage (stages II-IV) lung cancer. 

"Virtually all of the additional cancers detected represent over diagnosis," they report. 

"While lung cancer remains the most important cancer, overdiagnosis from CT screening is a very real problem," Dr. H. Gilbert Welch of Brigham and Women's Hospital, in Boston, who worked on the study, told Reuters Health by email. 

"Overdiagnosis is made more likely by a) screening a low-risk population (ie like Taiwanese women) and b) not having an organized screening program specifically designed to mitigate the problem (ie not requiring the growth protocols used in the randomized trials)," Dr. Welch noted. 

The team also found that, despite stable mortality, five-year survival more than doubled from 2004 to 2013, from 18% to 40%, "which is arguably the highest lung cancer survival rate in the world." 

The "spuriously high" five-year survival is biased by the increased LDCT detection of indolent early-stage lung cancers, they say. 

"Dramatic increases in five-year survival are typically seen as a benefit, but they instead may reflect harm: people being given needless diagnoses. That's why Taiwanese women now have the highest lung cancer survival rate in the world," Dr. Welch commented. 

"Although two major randomized trials have demonstrated reduced lung cancer mortality among heavy smokers, this benefit may be extrapolated to populations who are at lower risk for death due to lung cancer, and the data from Taiwan make clear the potential harms of this extrapolation," the researchers note in their paper. 

"It is hard for medical care to make well people better, but we can make them worse. That is what happens with overdiagnosis: an overdiagnosed patient can't benefit from intervention (because there is nothing to fix), but they can be harmed by it," Dr. Welch told Reuters Health. 

SOURCE: https://bit.ly/3IaFNAU JAMA Internal Medicine, online January 18, 2022. 

By Megan Brooks 

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