More False-Positive Lung Cancer Screens in Older Adults

Researchers have found that National Lung Screening Trial (NLST) participants aged 65 and older had a higher rate of false-positive screening results than younger participants, but a higher prevalence of cancer and positive predictive value (PPV).

A team including investigators from the National Cancer Institute, Washington University School of Medicine, Marshfield Clinic, and Duke University School of Medicine examined the results of the NLST low-dose computed tomography (LDCT) group by age, studying 19,612 participants aged 55 to 64 years (under-65 cohort) and 7,110 participants aged 65 to 74 years (65-plus cohort) at randomization. The researchers conducted 3 LDCT screenings, measuring demographics, smoking and medical history, screening examination adherence and results, diagnostic follow-up procedures and complications, lung cancer diagnoses, treatment, survival, and mortality.
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According to the authors, the aggregate false-positive rate was higher in the 65-plus cohort than in the under-65 cohort (27.7 percent versus 22 percent), and invasive diagnostic procedures after false-positive screening results were modestly more frequent in the older cohort (3.3 percent compared to 2.7 percent).

Complications from invasive procedures were low in both groups (9.8 percent in the under-65 cohort versus 8.5 percent in the 65-plus cohort), while prevalence and positive predictive value (PPV) were higher in the 65-plus cohort (PPV, 4.9 percent versus 3 percent). The researchers also saw that resection rates for screen-detected cancer were similar in both groups, finding a 75.6 percent resection rate in the under-65 group, and a 73.2 percent rate in the 65-and-up cohort.

Based on the findings from NLST, screen-eligible individuals between the ages of 65 and 74 “have a generally similar benefits-to-harms tradeoff for LDCT screening [to] subjects aged 55 to 64,” says Paul Pinsky, PhD, acting chief of the Early Detection Research Branch at the National Cancer Institute, and lead author of the study.

While the harms of screening, including the false positive rate and the rate of invasive procedures, may be modestly higher in those aged 65 and older, “the potential efficacy of screening is also greater, in terms of a higher yield of screening and a lower number needed to screen,” says Pinsky.

Yield of screening is the number of screen-detected cancers per 1,000 screens, and number needed to screen is the number of subjects needed to undergo screening to prevent 1 lung cancer death, he continues, adding that “a limitation of this study is that NLST subjects were generally healthier and had fewer co-morbidities than the overall U.S. population eligible for LDCT screening.”

Therefore, says Pinsky, “the above conclusions may only apply for a generally healthy screening population aged 65 and over.”

—Mark McGraw

Reference

Pinsky P, Gierada D, et al. National Lung Screening Trial Findings by Age. Ann Intern Med. 2014.