Low-Dose CT Screenings Associated With Lung Cancer Overdiagnosis in Nonsmoking Asian Women

An association was identified between low-dose CT (LDCT) screenings and notable overdiagnosis of lung cancer in non-smoking Asian women, according to findings from a population-based ecological cohort study.

From 2004 to 2018, following the introduction of LDCT, incidence of early lung cancer increased 6-fold for female patients. Specifically, the incidence increased from 2.3 to 14.4 per 100,000 individuals within that time period. However, investigators did not observe a change in incidence for patients with late-stage disease, which increased from 18.7 to 19.3 per 100,000.

“Although lung cancer is typically thought of as being uniformly deadly, concerns about screening-related lung cancer overdiagnosis have been long-standing. Evidence of overdiagnosis initially appeared with the long-term follow-up of 2 randomized trials of chest radiography screening. The concern became more prominent after an observational study of LDCT screening reporting similar rates of lung cancer detection in smokers and nonsmokers,” investigators wrote.

To assess the potential of over diagnosis following LDCT, investigators used data from the Taiwan National Cancer Registry to calculate incidence by stage. In particular, investigators collected evidence on 2 prerequisites of an effective screening program, including increased early-stage incidence and decreased late-stage incidence. Each indicate that screenings can detect cancer early and lead to a reduction in patients presenting with late-stage disease, respectively. In an environment of stable true cancer occurrence, overdiagnosis is likely when a rise in early-stage incidence is not followed by a concomitant decline.

A total of 12 million women were considered for the study, 57,898 of whom were diagnosed with lung cancer between 2004 and 2018. Additional findings from the study highlighted a rising incidence and stable mortality based on epidemiologic signature, which could be indicative of overdiagnosis. Moreover, 5 years prior to 2004, incidence and mortality both appeared stable, further highlighting that the primary analysis period notably encapsulates the onset of LDCT screenings.

Notably, lung cancer mortality in female patients decreased from 17 to 16 per 100,000 during the study period. Despite this, investigators reported a significant change in 5-year survival following diagnosis, doubling from 18% in 2004 to 40% in 2013. A trend in modest survival increases in high-income countries was observed, but Taiwan stands out more, investigators stated, due to having the highest lung cancer survival rate globally.

“The findings of this population-based ecological cohort study suggest that LDCT screening of mostly nonsmoking Asian women was associated with considerable overdiagnosis of lung cancer,” the investigators wrote. “Until randomized trials demonstrate value to lower-risk groups, our findings suggest that LDCT screening should be offered only to heavy smokers, and only following a balanced presentation of benefits and harms (which include not only overdiagnosis but also false-positive diagnosis, more incidental findings, more diagnostic procedures, and radiation-induced cancers).”

Reference

Gao W, Wen CP, Wu A, et al. Association of computed tomographic screening promotion with lung cancer overdiagnosis among Asian women. JAMA Intern Med. Published online January 18, 2022. doi:10.1001/jamainternmed.2021.7769