What Happens When Lung Cancer Screening Targets Nonsmokers?

Lung cancer screening promotion in a population with a low smoking prevalence was associated with a significant amount of overdiagnosis, an analysis involving women in Taiwan found.

In the population-wide study, incidence of early-stage lung cancer from 2004 to 2018 increased from 2.3 to 14.4 per 100,000 women (absolute difference 12.1, 95% CI 11.3-12.8). However, late-stage lung cancer incidence was virtually unchanged, inching from 18.7 to 19.3 cases per 100,000 women (absolute difference 0.6, 95% CI -0.5 to 1.7), Wayne Gao, PhD, of Taipei Medical University in Taiwan, and colleagues reported.

“To our knowledge, our findings represent the first evidence of LDCT [low-dose computed tomography]-induced lung cancer overdiagnosis at a population level,” Gao and colleagues wrote in JAMA Internal Medicine. “We surmise that virtually all the increased detection after the introduction of LDCT screening in 2004 represents overdiagnosis.”

A good screening program would detect cancer early, thereby increasing the early-stage incidence, and decrease the progression to advanced cancer, decreasing late-stage incidence, the researchers said.

During the study period, the 5-year lung cancer survival rate in women in Taiwan skyrocketed from 18% to 40%, far outpacing other high income countries, which have only seen “modest increases” in their lung cancer survival rates, according to the researchers. The country with the next highest lung cancer survival rate is Canada, at approximately 25%, noted Gao and colleagues.

“Although increased survival is often taken as evidence of the success of screening, survival statistics are biased by overdiagnosis,” the group cautioned.

Overall, from 2004 to 2018, lung cancer mortality among women in Taiwan decreased from 17 to 16 per 100,000, the study found.

Approximately 95% of Taiwanese women do not smoke. However, lung cancer screening programs that regularly screen nonsmokers have been expanding across Taiwan and other countries in Asia, including China, Japan, and South Korea, the researchers noted.

In the U.S., lung cancer screening recommendations with LDCT were broadened last year by the U.S. Preventive Services Task Force (USPSTF). The USPSTF now recommends that people ages 50 to 80 who have a 20 pack-year smoking history and who either currently smoke or have quit within the past 15 years undergo annual LDCT.

While hospitals and physicians in Taiwan can’t directly advertise screenings for lung cancer, screenings have been promoted in the media and on hospital websites beginning in 2004, Gao and colleagues said. These promotions often include images of young women entering CT scanners and language such as: “Avoid the tragedy of sudden death from terminal lung cancer like the stars (celebrities). People who have never done LDCT, especially women, should do it now,” according to the study.

Currently, Taiwan’s National Health Insurance (NHI), a compulsory single-payer system, does not cover LDCT screenings. However, it does cover downstream costs including “follow-up testing, biopsies, and surgical procedures,” the researchers said. From 2000 to 2018, claims for thoracotomies in women increased nearly tenfold, virtually all reflecting the growth of video-assisted thoracoscopic surgical procedures, the study group reported.

“These data highlight the financial incentives favoring opportunistic screening even without being a covered benefit; screening can be offered at reduced cost (even free) and generate downstream procedures that are reimbursed by the NHI,” the study authors wrote.

For their study, Gao’s group used data from the Taiwan National Cancer Registry, which included 57,898 women with a lung cancer diagnosis from 2004 to 2018. The median age of diagnosis over the study period dropped from 68 to 65 years of age.

The researchers noted that the true occurrence of lung cancer in Taiwan could be increasing, but this is an unlikely explanation as exposures to secondhand smoke have been decreasing and ambient air quality has been improving, they said.

Gao and co-authors acknowledged that their study could not directly measure the number of LDCT screenings over the study period since it is paid for out-of-pocket and not covered by Taiwan’s NHI. However, they did note that the number of LDCT scanners grew from 357 to 623 from 2003 to 2019.