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For those with lung cancer detected early through low-dose CT screening, high survival rates seen after a decade were maintained 20 years into the International ELCAP (I-ELCAP) program.

Of the people diagnosed with a first primary lung cancer, the 10-year lung cancer-specific survival rate of 81% plateaued and persisted through 20 years of annual screening, reported Claudia Henschke, PhD, MD, of the Icahn School of Medicine at Mount Sinai in New York City, and colleagues in .

The 20-year lung cancer-specific survival rate in the study reached 87% for both those diagnosed with clinical stage I lung cancer and those with the hybrid stage I definition. Survival was kept at 95% for people with resected pathologic T1aN0M0 lung cancers.

"Even after this long time interval they are not dying of their lung cancer," Henschke said in a statement. "And even if new lung cancers were found over time, as long as they continued with annual screening, they could be cured."

The survival curve plateau for estimating cure in lung cancer is generally considered to be reached at about 8 to 10 years after treatment, the researchers noted.

But as most lung cancer patients are diagnosed at later stages, when symptoms typically occur, the mean 5-year survival rate is 25.4% in the U.S., with a majority dying within a year of their diagnosis. Only one in five lung cancers are detected by screening.

"While screening doesn't prevent cancers from occurring, it is the major tool to identify lung cancers in their earliest stage when they can be cured," said Henschke. In the study, 81% of the screen-detected tumors were clinical stage I.

I-ELCAP has enrolled patients in annual low-dose CT screening since 1992. The program has been criticized for its lack of standardized eligibility criteria for screening -- controversially leaving the door open to people with only secondhand tobacco exposure -- among other limitations, such as an impractical protocol for following and managing lung nodules and the lack of a randomized comparator arm.

"However, it is also appropriate to recognize and heartily congratulate the study team on their impressive 30-year-long effort to further the understanding and implementation of lung cancer screening worldwide," wrote Lecia Sequist, MD, MPH, of Massachusetts General Hospital and Harvard Medical School in Boston, and Coral Olazagasti, MD, of the University of Miami.

"In addition, we now observe the field moving toward some areas that I-ELCAP embraced from the start. For example, a rise in lung cancer incidence among those who have not used tobacco forces us to rethink the epidemiology of lung cancer, and it is becoming clearer that environmental and genetic risk factors are important," the pair wrote in .

Philippe Grenier, MD, of Sorbonne University in Paris, stressed that despite its limitations, I-ELCAP supports the importance of regular CT screening for patients.

"As long as biomarkers or new innovative imaging techniques are not able to help detect early lung cancer, annual screening using low-dose CT remains the best method to reduce mortality from lung cancer," he wrote in . "In consideration of the recent and growing interest in cure rates of different cancers, the data reported ... are particularly welcome for both screening participants and health authorities."

Recently, the American Cancer Society widened the pool of individuals eligible for lung cancer screening, endorsing annual checks with low-dose CT for asymptomatic past or current smokers ages 50 to 80 years with a 20 pack‐year or greater smoking history.

The U.S. Preventive Services Task Force is more conservative, recommending annual lung cancer screening with low-dose CT in adults ages 50 to 80 years who have a 20 pack-year smoking history and who currently smoke or have quit within the past 15 years.

The I-ELCAP program enrolled 89,404 participants across Asia, Europe, and North America from 1992 to 2022. Included in the study were patients who were at least age 40 who had a history of smoking, were current smokers, or had been exposed to secondhand smoke.

The population was 45.6% women, the median patient age was 66 years, and the median patient smoking history was 43 pack-years. Most participants were white (92.3%).

The median follow-up time was 105 months. Of all participants, 1.4% would be diagnosed with primary small cell or non-small cell lung cancer from their annual screenings.

By smoking history, patients who had a 10 pack-year history or less, which included secondhand exposure, had a 20-year lung cancer-specific survival of 85%, while survival for those with a 10-29 pack-year history reached 83%, and those with a 30 pack-year or greater history reached 79% (P=0.26).

Through the end of 2022, 16.9% of participants had died from their lung cancer, yielding a rate of death from lung cancer of 18.8 deaths per 1,000 person-years.

Among the participants who had been diagnosed with lung cancer, 79.4% underwent surgical resection, about three-fourths of those within the first month following their diagnosis.

Notably, only 556 of the 1,257 patients with lung cancer had any available data past 10 years, Henschke and colleagues acknowledged. They also noted that lung cancer stage classifications have changed over time, and lung cancer diagnostic and treatment methods have improved. Another limitation of the study was the variable compliance to annual screening.