International lung cancer screening guidelines excluded 64.6% of patients in Korea ultimately diagnosed with the disease, according to a study published July 21 in JAMA Network Open. 

The finding comes from a retrospective, nationwide cohort study of 89,860 Korean patients diagnosed with lung cancer between 2013 and 2018, before the country's national screening program began, noted lead author Yeon Wook Kim, MD, PhD, of Seoul National University Bundang Hospital. 

“These findings suggest that population-specific strategies are needed to improve early detection among individuals not captured by current screening criteria,” the group wrote. 

Low-dose CT (LDCT) screening has demonstrated efficacy in reducing lung cancer mortality among individuals with substantial cigarette smoking exposure. Current national Korean screening criteria are current smokers aged 54 to 74 with at least 30 pack-years of smoking history who quit within the past 15 years or have not quit at all. Yet evidence directly comparing survival between screening-eligible and ineligible patients, including those with lighter smoking exposure or none at all, remains limited in Asia, the authors noted. 

To bridge the evidence gap, the group evaluated survival outcomes of Korean patients with lung cancer according to the 2023 American Cancer Society (ACS) screening criteria (aged 50 to 80 years old with a smoking history of 20 or more pack-years [PY]) compared with individuals with less than 20 PY, and persons with no smoking history within the same age range. 

According to the results, just 31,804 patients (35.4%) met screening eligibility criteria, while 39,627 (44.1%) had no smoking history and 4,232 (4.7%) were diagnosed before the age of 50. Among patients aged 50 to 80, screening eligibility differed markedly by sex, with 31,277 men (56.8%) and just 527 women (2.3%) meeting the screening criteria. Rates of distant metastatic disease at diagnosis were similar across groups, affecting 40.9% of the screening-eligible group, 41.1% of those with fewer than 20 pack-years, and 36.9% of those with no smoking history. 

Additionally, patients with lighter smoking exposure or no smoking history had better survival than those who met screening criteria. Compared with the screening-eligible group, those with fewer than 20 pack-years had a 5% lower risk of all-cause mortality and a 4% lower risk of lung cancer-specific mortality, while never-smokers had a 14% lower risk of both all-cause mortality and lung cancer-specific mortality. 

“Our data reflect the distinct epidemiology of lung cancer in Asia, which bears the highest global burden of the disease and related deaths, with a particularly high proportion of diagnoses occurring among persons with no smoking history,” the group wrote. 

In an accompanying editorial, Mattias Johansson, PhD, and Xiaoshuang Feng, PhD, both of the International Agency for Research on Cancer in Lyon, France, wrote that future risk assessment should move beyond smoking history alone and incorporate factors such as demographics, occupation, medical and family history, and environmental exposures. 

While several risk prediction models have been developed in East Asian populations, prospective validation in unscreened populations is still needed prior to implementation, they noted. 

“These methods are needed before expanding eligibility outside current criteria, if we want to ensure that LDCT screening will continue to do more good than harm,” Johansson and Feng wrote. 

The full study is available here.