Forget ‘Pack-Years’ for Lung Cancer Screening Eligibility, Study Suggests

Dropping pack-years for lung cancer screening eligibility in favor of a simpler 20-year history of smoking could substantially increase the number of cancers detected and eliminate racial disparities as well, according to an analysis of smokers from two large cohort studies.

Under current screening criteria from the U.S. Preventive Services Task Force (USPSTF), which call for a 20-pack-year history of smoking, researchers found that 58% of Black patients with lung cancer in the Southern Community Cohort Study (SCCS) would have been eligible for screening, compared with 74% of white patients with lung cancer in SCCS.

But these percentages would increase to 85.3% and 82%, respectively, with the proposed 20-year duration of smoking criteria, “thus eliminating the racial disparity in screening eligibility,” reported Chi-Fu Jeffrey Yang, MD, of Massachusetts General Hospital in Boston, and colleagues in the Journal of Clinical Oncology.

Additionally, an analysis of the Black Women’s Health Study (BWHS) showed a switch to the simpler requirement would have increased the percentage of Black women who qualified for screening from 43% to 64%.

“These findings challenge the use of pack-year smoking history in determining lung cancer screening eligibility and support the use of smoking duration cutoffs instead as a simple yet effective change to increase the sensitivity of the guideline and improve equity in opportunities for screening,” the researchers concluded.

However, while the proposed change would make it easier to identify eligible screening participants and increase sensitivity, the benefits came with a considerable tradeoff — a “notable decrease in specificity,” wrote Hasmeena Kathuria, MD, and Renda Soylemez Wiener, MD, MPH, both of the Boston University Chobanian & Avedisian School of Medicine, in an accompanying editorial.

In the two cohorts, the specificity with the pack-year cutoff (under current USPSTF guidelines) versus the proposed duration-of-smoking cutoff decreased as follows:

• Black people in SCCS: 63.6% to 29.3%
• White people in the SCCS: 49.7% to 38.5%
• Black women in the BWHS: 86.8% to 71.7%

“The lower specificity suggests that the proposed criteria would expand screening to many low-risk people who will never develop lung cancer, increasing the number exposed to screening-related harms,” the editorialists said.

Yang and colleagues acknowledged that under their proposed guidelines a higher percentage of Black individuals would become eligible for screening and be exposed to screening-related harms, such as false-positive findings leading to unnecessary tests, invasive procedures, and treatment.

“They will not, however, be at greater risk of harm than white individuals,” the study authors wrote. “Furthermore, the very low risk of harm from lung cancer screening must be considered, as always, in the context of the life-saving potential of early lung cancer detection.”

The 2021 USPSTF guidelines lowered the age for the start of screening via low-dose CT by 5 years and redefined “heavy smoker” as a 20 pack-year history (one pack of cigarettes daily for 20 years). This was a reduction of 10 pack-years from the prior recommendation, a change designed to reduce screening disparities since Black people and women tend to smoke fewer cigarettes than white men.

In explaining the rationale behind the study, the authors noted that there have been no studies comparing the use of pack-year smoking history with other measures of tobacco exposure to select individuals for lung cancer screening, and that some studies have shown that smoking duration is more strongly associated with lung cancer risk than smoking intensity.

“The use of a pack-year smoking history cutoff to select individuals for screening may exclude many individuals at high risk for lung cancer by underestimating lung cancer risk among those who smoke less intensely (i.e., fewer cigarettes per day), such as individuals from racial and ethnic minority groups,” they wrote.

Kathuria and Wiener also suggested that lung cancer screening is just “one piece of the puzzle” when it comes to inequities in lung cancer mortality, and that racial disparities among Black and white people regarding screening uptake, adherence, and smoking quit rates should also be addressed.

By doing so, “we can begin to improve lung cancer mortality rates for everyone,” they said.

The SCCS included 49,703 men and women, of whom 67.6% were Black (51% male) and 32.4% were white (43% male). During follow-up, 4.0% of Black and 5.0% of white individuals were diagnosed with primary lung cancer.

The BWHS included 22,126 Black women with a smoking history, 2.2% of whom were diagnosed with lung cancer during follow-up.

More than 80% of the individuals in both studies were between the ages of 50 and 80 at last follow-up.

The authors acknowledged the study had limitations, including the possibility that smoking exposure was misclassified since smoking information was self-reported. Individuals in the SCCS and BWHS may not be representative of all people at high risk for lung cancer in the U.S., they added.

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