Revised guidelines support low-dose CT screening for patients between ages 50 and 80 with 20-pack year smoking histories – a move that lowers the screening age and, potentially, incorporates more high-risk individuals.
The U.S. Preventive Services Task Force (USPSTF) has revised its existing lung cancer screening recommendations with two major changes – its new guidance lowers screening age and incorporates patients with a shorter smoking history.
Published today in JAMA, the new recommendation now calls for patients between ages 50 and 80 who have 20-year pack histories to undergo annual low-dose CT (LDCT) screening for lung cancer. This is a change from the 2013 recommendation that referred to patients ages 55 to 80 with 30-year pack histories.
The USPSTF gave this recommendation a B grade, indicating it is based on, at least, fair evidence that it can positively impact outcomes and should be applied to eligible patients.
“The USPSTF concludes with moderate certainty that annual screening for lung cancer with LDCT has a moderate net benefit in persons at high risk of lung cancer based on age, total cumulative exposure to tobacco smoke, and years since quitting,” the task force wrote in its recommendation statement.
The group maintains that screening can be stopped at age 80 or when a patient has not smoked within the past 15 years. Screening can also be halted if the patient develops a condition that significantly limits his or her life expectancy or if they decide to undergo curative surgery.
Lung cancer is the leading cause of cancer death in the United States with nearly 228,820 diagnosed cases and 135,720 deaths in 2020 alone. Smokers are at a 20-times higher risk of developing the disease than non-smokers, and the risk rises with age with most cases detected around age 70.
The five-year survival rate among patients is poor – 20.5 percent – but, prognosis and outcomes are better with earlier detection. Unfortunately, utilization of LDCT for lung cancer has been disappointingly low. According to a recently published study on screening rates from the American Lung Association, only 5.7 percent of the 8 million people eligible for screening actually participate. Consequently, the USPSTF set out to revise the recommendation with the goal of pinpointing the optimal screening range and interval that can maximize positive outcomes.
Making this change also stands to expand screening eligibility for groups of smokers who, historically, have not received LDCT screening because they do not have as intense or long of a smoking history, such as women and racial and ethnic minorities.
For example, said Anupam Basu, M.D., a diagnostic radiologist in Cook County Health, who conducted a study, published in the Journal of the American College of Radiology that examined the lung cancer screening threshold, this change has the potential to make a significant difference with African American smokers. Not only does this group have a higher incidence of lung cancer, but they also report worse outcomes – even though they mostly have smoking histories of fewer than 30 pack years.
“Lowering the pack-year history to 20 years is a good thing. Obviously, it will make more African Americans – and other racial and ethnic minorities – eligible to be screened,” he explained. “In the major literature on lung cancer screening, African Americans have been understudied. Given their lower pack-year histories, dropping the threshold will have some real benefits.”
Making the Revisions
To pinpoint the most appropriate age to begin screening and the best screening interval, the task force used the Cancer Intervention and Surveillance Modeling Network (CISNET). The CISNET analysis revealed that dropping the pack-year threshold could be associated with a reduction in lung cancer deaths by 13 percent instead of the 9.8 percent created by a 30 pack-year history.
They also used the findings of two additional studies published today in JAMA to revise their official recommendation – one that evaluated LDCT performance and another that assessed the scan’s benefits and risks.
In a review of 223 publications and seven randomized clinical trials, including the National Lung Screening Trial (NLST) and the NELSON Trial, a multi-institutional team of investigators led by Daniel E. Jonas, M.D., MPH, from the internal medicine department at The Ohio State University, observed screening rates for 86,486 patients.
Based on their analysis, they determined patients who undergo LDCT experience more benefit than do those who have ultrasound screening. Their assessment of the NLST determined an incidence rate ratio (IRR) of 0.85 for the reduction of lung cancer mortality, and the NELSON trial had an IRR of 0.75.
Alongside that screening efficacy, though, comes both benefits and risks. In the second study, conducted by another multi-institutional team led by Rafael Meza, Ph.D., from the epidemiology department at the University of Michigan, researchers compared outcomes for patients with 20-pack year histories to those with 30-pack year histories. A pack year equates to 20 cigarettes per day for a year.
Meza’s team found that, in addition to increased eligibility for screening, 20-pack year patients also avoided more deaths – 469-to-588 deaths per 100,000 persons versus 381 per 100,000 for 30-pack year patients. They also gained more life years – 6,018-to-7,596 years per 100,000 patients compared with 4,882 per 100,000 for 30-pack year patients.
But, they also saw lowering the eligibility age resulted in more false positives – 1.9-to-2.5 cases per person versus 1.9 for 30-pack year patients, as well as more lung cancer overdiagnosis – 83-to-94 cases per 100,000 versus 69 per 100,000 for 30-pack year patients. Additionally, they determined that lowering eligibility age resulted in more radiation-induced cancer deaths, increasing the rate to 29-to-42.5 deaths per 100,000 patients versus 20.6 per 100,000 among the 30-pack year group.
What does the recommendation change mean?
Overall, widening the eligibility age and including high-risk patients with fewer pack years stands to increase the number of patients who qualify for LDCT by 81 percent, said a team of investigators led by Ethan Basch, M.D. from the Lineberger Comprehensive Cancer Center at the University of North Carolina at Chapel Hill in an accompanying editorial. If successfully implemented, it will add 6.4 million adults to the potential screening group.
Basch’s team reiterated that the most significant improvements are likely to be seen among women and racial and ethnic minority groups who have traditionally been under-screened because their smoking history fell below the 30-pack year threshold.
But, additional barriers to appropriate screening levels still exist, they said. For the most part, simply being able to find a facility for screening – and, then, affording it – can keep a patient from receiving LDCT.
“While expanded eligibility criteria are an important step toward equity, barriers to screening, including lack of insurance coverage and physical access to high-quality screening programs, highlight the complex implementation issues to be address,” they wrote, noting that guidelines and evidence alone are not enough to overcome the screening obstacles that exist.
Sometimes, however, leading a patient to have a screening can be the most difficult part. This is where shared decision-making can be important, said a team led by Richard M. Hoffman, M.D., MPH, from the division of general internal medicine at the University of Iowa Carver College of Medicine, in another accompanying editorial. Providing counseling around the screening, discussing the benefits and risks, and talking about a patients individual circumstances can go a long way toward encouraging a patient to get screened and to stick with it.
“The purpose of shared decision-making visits is not to influence overall screening rates, but to ensure that the values and preferences of an informed patient are part of the screening decision,” Hoffman’s team wrote. “[But], providing high-quality decision support is a patient-centered approach that may potentially increasing screening uptake or tobacco cessation in vulnerable populations.”
Ultimately, said both teams led by Basch and Hoffman, this USPSTF change can potentially lead to greater benefits for patients at high-risk for lung cancer, but it is not the final step.
“The 2021 USPSTF recommendation statement represents a leap forward in evidence and offers promise to prevent more cancer deaths and address screening disparities,” Basch’s team wrote. “But, the greatest work lies ahead to ensure this promise is actualized.”
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