Study Suggests Lung Cancer Screening Criteria May Not Capture All Smokers Who Need It

Eligibility criteria set by the Centers for Medicare & Medicaid Services (CMS) for coverage of low-dose computed tomography (LDCT) for individuals deemed at high risk for lung cancer may actually exclude many potential lung cancer patients who would benefit from screening, according to a new study.

The findings, published in the Journal of the American Medical Association, indicate that efforts to get long-term smokers to quit in recent decades make some former long-term smokers ineligible for screening, because they have not smoked for more than 15 years.

In the study, by Ping Yang MD, and colleagues at the Mayo Clinic in Rochester, Minn., researchers evaluated trends in the proportion of patients with lung cancer who meet the US Preventive Services Task Force (USPSTF) criteria as being at high risk for lung cancer. CMS used the USPSTF criteria as the basis for its coverage determination.

Researchers looked at 140,000 residents in Olmstead County, Minn., aged 20 or older, from 1984 through 2011. All confirmed cases of lung cancer were identified using the Rochester Epidemiology Project database, adjusting for age and gender distribution in the US population in 2000.

The proportion of cases meeting USPSTF criteria was identified and represented asymptomatic adults aged 55 to 80 years with a 30 pack—year smoking history. This means the person smoked the equivalent of one pack a day for 30 years; a person could also have smoked two packs a day for 15 years. To be screened, a person must be a current smoker or have quit within the past 15 years. Under the Medicare criteria, the age cutoff for LDCT coverage is 77 years.

Researchers identified 1351 patients with a new diagnosis of primary lung cancer between 1984 and 2011. However, the proportion of patients with lung cancer who smoked more than 30 pack-years declined, and the proportion of former smokers, especially those who quit more than 15 years ago, increased.

Of note, the share of lung cancer patients meeting the USPSTF criteria declined over time, with 57 percent of patients eligible for screening from 1984 to 1990 and only 43 percent eligible from 2005 to 2011. The drop-off in eligibility was greater among women—from 52 percent to 37 percent; for men the drop-off was 60 percent to 50 percent.

“Our findings may reflect a temporal change in smoking patterns in which the proportion of adults with a 30 pack—year smoking history and having quit within 15 years declined,” the authors write. “The decline in the proportion of patients meeting USPSTF high-risk criteria indicates that an increasing number of patients with lung cancer would not have been candidates for screening. More sensitive screening criteria may need to be identified while balancing the potential harm from computed tomography.”

CMS’ decision to screen current and former smokers for lung cancer was based on the results of the National Lung Screening Protocol Trial Protocol, which found that patients who received screening had a 15% to 20% lower risk of dying from lung cancer; results published in 2013 showed that targeting screening toward those at greatest risk produced the most effective results.