High-risk patients older than 65 years derive slightly more benefit from low-dose CT screening for lung cancer than younger patients do, according to a report published online Sept. 8 in the Annals of Internal Medicine.
In a secondary analysis of data from the National Lung Screening Trial, low-dose CT (LDCT) screening’s positive predictive value, a measure of screening efficiency, was higher in older patients than in those younger than 65. However, older patients also had slightly greater harms from LDCT screening, mainly because of a slightly higher rate of false-positive results, said Paul F. Pinsky, Ph.D., of the National Cancer Institute and his associates.
They examined this issue because the Centers for Medicare & Medicaid Services has raised the question of whether to cover LDCT costs in this age group, citing concerns that harms may outweigh benefits in the elderly. The National Lung Screening Trial was the primary source of evidence that the screening reduces lung cancer–specific mortality in patients aged 55-74 years, but only 25% of the participants were older than 65. It has been proposed that older patients, who tend to have more comorbid conditions than younger patients, might incur more complications from diagnostic work-ups, might be less eligible for curative surgery for screen-detected cancer, and might have elevated postsurgical mortality, which could tip the balance away from benefit and toward harm.
Dr. Pinsky and his associates assessed several facets of LDCT screening according to the age of the participants, comparing the National Lung Screening Trial’s findings for 19,612 aged 55-64 years against those for 7,110 patients aged 65-74 years at baseline. All the participants underwent three annual LDCT screens and were followed for a median of 6.5 years to ascertain lung cancer mortality.
The sensitivity of LDCT in detecting lung cancers was similar between the two age groups, at 93.2% in the under 65 and 94.3% in the over 65 groups. LDCT’s positive predictive value was significantly higher in the older group (4.9%) than in the younger group (3.0%), mainly because the older group had a substantially higher prevalence of lung cancer (1.5% vs 0.7%). Five-year lung cancer–specific survival was only modestly higher for the under 65 group (64%) than for the over 65 group (55%), the investigators reported (Ann. Intern. Med. 2014 Sept. 8 [doi10.7326/M14-1484 ]).
Similar proportions of each group underwent lung resection – 75.6% of the under 65 and 73.2% of the over 65 groups. In addition, postsurgical mortality at 90 days was similarly low, at 1.8% in the under 65 and 1.0% in the over 65 groups. So the concern that many more older than younger patients would be ineligible for curative surgery proved to be unfounded, as did the concern that older patients would experience significantly more harm from resection than younger patients.
On the "harm" side of the balance, the percentage of false-positive results was higher in the older group (27.7% vs 22.0%), and invasive procedures after false-positive results were slightly more frequent as well (3.3% vs 2.7%). However, the rates of complications resulting from these procedures were similarly low, at 9.8% for the under 65 group and 8.5% for the over 65 group.
"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 evidence, if needed," Dr. Pinsky and his associates wrote.
They added that their analysis was limited by the fact that the upper age limit in the National Lung Screening Trial was only 74 years. "This precluded analysis of how persons in their later 70s and 80s fared with LDCT screening," they said.
This study was supported by the National Cancer Institute. Dr. Pinsky had no relevant disclosures to report and coauthors reported financial disclosures involving the NCI and various biotechnology companies.