Trends in the Proportion of Patients With Lung Cancer Meeting Screening Criteria

Lung cancer screening using low-dose computed tomography is recommended for high-risk individuals by professional associations, including the US Preventive Services Task Force (USPSTF).¹ The implications of the USPSTF screening criteria were investigated in a well-defined population retrospectively over 28 years to demonstrate trends in the proportion of patients with lung cancer meeting the criteria.

The cohort contained all Olmsted County, Minnesota, residents older than 20 years from 1984 through 2011, comprising approximately 140 000 people, of whom 83% were non-Hispanic white and socioeconomically similar to the Midwestern US population.² All pathologically confirmed incident cases of primary lung cancer were identified using the Rochester Epidemiology Project database; the project has maintained a comprehensive medical records linkage system for more than 60 years based on hospital adaptation of the International Classification of Diseases and International Classification of Diseases, Ninth Revision, codes.^2,3 Patient characteristics were extracted with minimal missing data or loss to follow up.³ This study was approved by the Mayo Clinic and Olmsted Medical Center institutional review boards with a waiver of informed consent.

Trends in lung cancer incidence rates were determined based on decennial census data adjusted for the age and sex distribution of the US population in 2000. Cases were grouped into 4 calendar-year intervals (each 7 years) when assessing secular trends to minimize the annual rate fluctuations. Assuming a Poisson distribution, 95% confidence intervals for incidence rates were calculated with generalized linear models using the Poisson error structure and a log-link function.^4,5

The proportion of cases meeting USPSTF screening criteria were identified. The criteria included asymptomatic adults aged 55 to 80 years, having a 30 pack-year smoking history, and currently smoking or having quit within the past 15 years.¹ The Cochran-Armitage trend test was used for comparing proportions. Two-sided P < .05 was considered statistically significant. Analyses were performed using SAS version 9.3 (SAS Institute Inc).

There were 1351 patients with incident primary lung cancer between 1984 and 2011. The mean (SD) age was 68.1 (11.3) years and 54.9% were male. The age- and sex-adjusted incidence rate decreased from 52.3 (95% CI, 45.8-58.7) per 100 000 person-years in 1984-1990 to 44.1 (95% CI, 39.7-48.5) per 100 000 person-years in 2005-2011 (P < .001; Table). Trend analyses showed a decline in men but not women. 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 smoking more than 15 years ago, increased.

We observed a decline in the relative proportion of patients with lung cancer meeting the USPSTF criteria overall from 56.8% (95% CI, 50.8%-62.9%) in 1984-1990 to 43.3% (95% CI, 38.4%-48.2%) in 2005-2011 (P < .001; Figure). The proportion of patients who would have been eligible under the criteria decreased in women from 52.3% (95% CI, 42.9%-61.8%) to 36.6% (95% CI, 29.8%-43.4%) (P = .005) and in men from 60.0% (95% CI, 52.2%-67.8%) to 49.7% (95% CI, 42.8%-56.7%) (P = .03).

The proportion of patients with lung cancer in Olmsted County meeting the USPSTF screening criteria decreased significantly between 1984 and 2011, with only 37% of female and 50% of male patients eligible for screening during the most recent interval. 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 secular trends in lung cancer incidence rates in Olmsted County are comparable with US Surveillance, Epidemiology and End Results registry data,⁶ but may not be generalizable to the entire US population.

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.

Corresponding Author: Ping Yang MD, PhD, Division of Epidemiology, Department of Health Sciences Research, Mayo Clinic, 200 First St SW, Rochester, MN 55905 (yang.ping@mayo.edu).

Author Contributions: Drs Wang and Yang had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Wang, Midthun, Yang.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Wang, Midthun, Deng, Zhang, Yang.

Critical revision of the manuscript for important intellectual content: Wang, Midthun, Wampfler, Stoddard, Yang.

Statistical analysis: Wang, Midthun, Wampfler, Deng, Zhang, Yang.

Obtained funding: Yang.

Administrative, technical, or material support: Wang, Yang.

Study supervision: Midthun, Yang.

Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This study was supported by grants R03 CA77118, R01 CA80127, and R01 CA84354 from the National Institutes of Health, grant R01 AG034676 from the National Institute on Aging, and funding from the Mayo Clinic Foundation.

Role of the Sponsor: The National Institutes of Health, the National Institute on Aging, and the Mayo Clinic Foundation had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Additional Contributions: We thank Barbara A. Abbott, Jennifer L. St Sauver, PhD, and Walter A. Rocca, MD (Department of Health Sciences Research, Mayo Clinic), and Barbara P. Yawn, MD (Department of Research, Olmsted Medical Center), for their assistance in preparing the manuscript. We also appreciate Khadija Idiris for her technical assistance with the manuscript. No compensation was received by any of these individuals.