Low-Dose CT Lung Cancer Screenings in 20 to 29 Pack-Year Smokers
The potential risks and harms of low-dose computed tomography lung cancer screening in current 20 to 29 pack-year smokers needs to be assessed before recommending such screening to this group, according to a study published by Pinsky and Kramer in the Journal of the National Cancer Institute. (The pack-year is calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked; thus, 1 pack-year is equal to smoking 20 cigarettes [1 pack] per day for 1 year.)
Recently, recommendations made by the U.S. Preventive Services Task Force (USPSTF) stated that eligibility to have low-dose computed tomography lung cancer screening required a cigarette smoking history of 30-plus pack-years, and, if a former smoker, having quit smoking within the last 15 years in patients aged 55 to 80.
While these recommendations matched the eligibility criteria of the National Lung Screening Trial (NLST)—except that the upper age limit for entering the NLST was 74—guidelines made by the National Comprehensive Cancer Network (NCCN) recommend that those with the NLST smoking history criteria or a 20-plus pack-year smoking history and one additional lung cancer risk factor, such as occupational exposure or pulmonary disease history, could also be eligible for screening. While many studies have shown a much lower lung cancer risk in persons who have quit smoking, the risk for those who have smoked 20 to 29 pack-years remains unknown.
Study Findings
In order to determine the risk of lung cancer in those who smoked 20 to 29 pack-years, Paul F. Pinsky, PhD, and Barnett S. Kramer, PhD, both of the National Cancer Institute, looked at data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a randomly assigned screening trial of subjects aged 55 to 74 years with chest x-rays used for lung cancer. Subjects completed a baseline questionnaire that asked questions regarding smoking history. The researchers also used data from the National Health Interview Survey (NHIS), which looked at smoking history, race/ethnicity, and the demographic profiles of various high-risk smoking history categories. Models were adjusted to account for age and sex of the subjects.
The researchers found that the risk of lung cancer among 20 to 29 pack-year current smokers was similar to that of 30-plus pack-year former smokers who meet the current guidelines for low-dose computed tomography screening set by the USPSTF. Further, based on the NHIS data, current 20 to 29 pack-year smokers were more likely to be female and to belong to racial/ethnic minorities than were those meeting the current USPSTF guidelines.
Despite these findings, the researchers feel that the guidelines should be approached cautiously in terms of recommending screening to 20 to 29 pack-year current smokers. “This group was not included in the NLST, so there is the untested assumption that the trial's mortality benefit can be extrapolated to them,” the researchers wrote. “Until [low-dose computed tomography] screening performance in population settings is better understood, expansion of screening to additional populations may incur unanticipated harms.”
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
