A secondary analysis of data from the National Lung Screening Trial (NLST) reveals an even greater potential benefit in the Medicare-aged population than in the broader, 55-to-74 age group, with screen-detected cancer rates in the 65+ age group more than twice that of the 55–64 age group.

Published online first in the Annals of Internal Medicine, the study utilizes NLST participants from the low-dose CT (LDCT) cohort only and compares baseline characteristics, screening results and downstream outcomes for the under-65 cohort versus the 65+ cohort.

Of the 26,722 participants randomly assigned to the LDCT group, 7,110 were in the 65+ cohort. The authors note that the 65+ cohort had a greater number of co-morbidities than the under 65 group, and 17.4% of the older participants had a history of chronic obstructive pulmonary disease versus 11.8% in the younger cohort.

More significantly, the rates of positive and false positive screens were higher in the 65+ cohort in each round of screening, as was the positive predictive value of the study in the 65+ cohort (4.9% versus 3%) due to the substantially higher prevalence of lung cancer in the 65+ cohort (1.5% versus .7%).

The percentage of patients with negative results but clinically significant findings also was higher in the 65+ cohort (9.2%) versus the under-65 group (6.9%).

The authors found very little difference between the two cohorts in:

• sensitivity of LDCT (93.2% in the under-65 cohort versus 94.3% in the 65+ cohort),

• stage and histology of cancer at screen detection,

• proportion of resections (75.6% in the under-65 cohort versus 73.2% in the 65+ group), and

• post-surgical mortality (1.8% in the under-65 cohort versus 1% in the 65+ cohort).

In their discussion, the authors wrote: “In general, cancer screening is more efficient in higher-risk populations because persons can only benefit from it if they develop the cancer of interest, whereas the harms of screening are usually relatively constant across the cancer risk spectrum. After smoking, arguably the next most important risk factor for lung cancer is age.”

They conclude: “It is difficult to predict how LDCT screening for lung cancer will disseminate in the Medicare-eligible population, regardless of whether it is covered by Medicare. Its use may spread to persons with little chance of benefit and some chance of harm, although this risk exists for those in younger age groups as well.

“Going forward, monitoring and assessing the relative performance of LDCT screening in older persons will be critical to more fully understand its risks and benefits when it is done outside the clinical trial setting and to modify recommendations on the basis of the evidence if needed.”

Lead author Paul Pinsky, PhD, MPH, has a special interest in the translation of research to practice as acting chief, early detection research group, division of cancer prevention, National Cancer Institute.