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BOSTON -- Whether low-dose CT screening for lung cancer should be expanded to include people who quit smoking more than 15 years ago, as the American Cancer Society (ACS) now recommends, was the topic of much debate here.

ACS guidance previously said that lung screening should not begin if someone quit smoking more than 15 years ago or should stop once that point is reached. But in November 2023, the ACS issued new screening guidelines that removed that criteria, expanded the age range for eligibility from 55-74 to 50-80 years, and decreased the number of pack-years for current and former smokers from 30 or more to 20 or more.

Although otherwise in agreement, the current U.S. Preventive Services Task Force (USPSTF) recommendations, updated in 2021, maintain the years since smoking criteria.

On the Pro Side

Nina Thomas, MD, of the University of Colorado in Aurora, made the case for implementing the new ACS recommendations at the CHEST annual meeting hosted by the American College of Chest Physicians.

The changes were based on an from the Cancer Intervention and Surveillance Modeling Network that estimated that the 2021 USPSTF recommendations could increase screening-detected lung cancers by 21%, and could expand screening and improve early lung cancer diagnoses for women and minority populations.

The ACS also conducted its own of available research and found that lung cancer incidence remained elevated beyond 15 years since quitting, although it declined to a certain extent, Thomas said.

"Mortality risk still remains high after 15 years -- about five times higher -- for patients [with] 15 to 20 years since quitting ... there's nothing magical about the number 15," she noted.

She also pointed out that, because of aging, absolute lung cancer risk beyond the 15 years since quitting. Removing the quit-year criterion could increase the proportion of lung cancer deaths prevented from about 64% to 74%, she said.

Furthermore, the review also showed that removing the 15 years since quitting criterion had the potential to expand eligibility for both Black and white patients.

Thomas said previous studies have reviewed the potential for harm from radiation associated with low-dose CT scans. "When we talk about weighing the true harm of low-dose CT screening with the benefit of early diagnosis of lung cancer ...for annual screening for patients ages 50 to 79, with at least a 20 pack-year smoking history, the benefit-to-radiation risk ratio is actually ," she explained.

"These simplified ACS criteria allow us to cast a wider net to identify more patients who would benefit from lung cancer screening," she argued. "That being said, all these patients should be getting a shared decision-making conversation, [and clinicians] should be incorporating risk models to determine who truly benefits, and [should] assess comorbidities and life expectancy to weed out the patients who probably won't benefit."

On the Con Side

On the other side of the debate, Eduardo Nunez, MD, of the University of Massachusetts Chan School of Medicine-Baystate in Springfield, questioned the benefits of adopting the new ACS recommendations.

Optimizing patient selection is critical to realize any benefit to lung cancer screening, he said. "That means screening individuals who are likely to benefit from early detection of lung cancer and not screening those less likely to benefit," such as patients with low overall lung cancer risk or those at higher lung cancer risk but with limited life expectancy or frailty.

"Extending the eligibility criteria would disproportionally increase the share of both of these [latter] groups," Nunez pointed out.

People who self-report fair or poor health are actually more likely to undergo cancer screening, even though they are less likely to benefit from treatment, Nunez said.

In addition, providers overestimate the benefits of screening at a population level, and they often don't weigh benefits versus risks for individual patients, he explained.

"We've had providers tell us 'we're screening a high-risk population. I personally feel the benefits outweigh the risks, so I often don't go into that so much with the patients,'" he said. "We have other providers say, 'as long as they can lie down in the machine, they can get screened.'"

There is a lack of clinical trial data to establish a clear risk-benefit ratio for expanding lung cancer screening. According to National Lung Screening Trial data, the to prevent one death is 320, he pointed out.

Nunez also warned that the new ACS recommendations are likely to increase overdiagnoses of lung cancer, "meaning, detecting a cancer that's not going to impact someone's life." Modeling studies have estimated that the rate of overdiagnosis per screening-detected lung cancer is , he said.

Another potential pitfall of lung cancer screening is false-positives. of individuals who undergo screening will have a nodule detected, but almost all are benign. "That can actually be pretty distressing for patients," Nunez said. In addition, complications can arise when a positive screen triggers further downstream procedures.

Although the new ACS recommendations increase the number of adults eligible for screening, they may not improve access to vulnerable, at-risk populations who receive Medicaid or have no health insurance -- circumstances that are more common in minority populations, he noted.

On top of these drawbacks, existing guidelines are already poorly understood by patients and providers, Nunez said. This is reflected in low uptake, with just 5% to 18% of eligible people getting screened. "Frequently changing guidelines just cause more confusion," he added.

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