A big question mark sits over the topic of low-dose CT lung cancer screening. Since the April meeting of the Medicare Evidence Development & Coverage Advisory Committee (MedCAC), many are left wondering about the controversy over low-dose CT lung cancer screening (LDCT) and the eventual decision that will be made regarding Medicare reimbursement for screening. What does the research really reveal about its effectiveness, and what do proponents and opponents to reimbursement say about the contentious topic?
Back in December 2013, the U.S. Preventive Services Task Force (USPSTF) recommended annual screening with LDCT for asymptomatic individuals between the ages of 55 and 80 who have a 30 pack-year history of smoking and currently smoke or have quit within the last 15 years. The recommendation, labeled as grade “B,” stated screening be discontinued once a patient has ceased smoking for 15 years or develops a health problem that drastically limits his or her life expectancy or willingness to undergo curative lung surgery. With a grade “B” status, private insurers must cover the procedure without a co-pay under the Affordable Care Act. The healthcare reform law does not, however, force Medicare to provide full national coverage for the recommendation. Here enters the conflict.
The USPSTF’s recommendation was largely based upon the National Lung Screening Trial (NLST), which found that annual LDCT scans could reduce the chances of dying from lung cancer by up to 20 percent in the high-risk patient population. The trial enrolled 53,454 current or former heavy smokers from 33 sites and coordinating centers across the United States.
Participants in the trial were randomized to three annual screens with either low-dose helical CT or a single-view chest X-ray. Lung cancer incidence per 100,000 person-years was 645 in the LDCT arm and 572 in the chest X-ray arm. Lung cancer mortality was 247 per 100,000 person-years in the LDCT arm and 309 in the chest X-ray arm, demonstrating a 20 percent reduction in lung cancer mortality in the LDCT arm. All-cause mortality was reduced by 6.7 percent for participants who underwent LDCT compared to those who got X-rays.
On average during the three rounds of screening, 24.2 percent of the LDCT screens were positive and 6.9 percent of the chest X-rays were positive. In both arms, the majority of positive scans led to more screening. Across all rounds, the false-positive rate was 96.4 percent for the LDCT tests and 94.5 percent for the chest X-rays.
Considering all pieces of the screening puzzle
While the results of the NLST show promise for reducing mortality among this high-risk population, concerns loom over overdiagnosis. A study led by Edward F. Patz, Jr., MD, of Duke University School of Medicine in Durham, N.C., examined data from the NLST to estimate overdiagnosis in the cancers detected by LDCT.
The study’s results indicated approximately 20 percent of all the lung cancers found were attributed to overdiagnosis; these cancers would never have affected the patient’s outcome. Patz attests that overdiagnosis should be one limitation to consider when patients are deciding whether or not to undergo screening.
“In the future, once there are better biomarkers and imaging techniques to predict which individuals with a diagnosis of lung cancer will have more or less aggressive disease, treatment options can be optimized, and a mass screening program will be more efficient and effective,” wrote Patz and colleagues in the study, which was published online December 9, 2013, in JAMA Internal Medicine.
Patz says, however, that no strides ready to be implemented in clinical practice have been made in this realm yet. “I think this is an area that we need more resources and research in to really understand which cancers have a fairly benign phenotype and will not likely affect the patient,” he says.
In terms of the study’s implications on the future of LDCT, Patz remarks that overdiagnosis is one potential limitation of any screening test.
“Screening will almost always find some disease that may not become clinically apparent,” says Patz. “The more you interrogate, the more you’re going to find abnormalities that you’re not going to know what to do with.”
To craft a public policy regarding screening, Patz suggests considering all pieces of the puzzle involved, including overdiagnosis and false-positives. “It appears that one of the MedCAC concerns was that there are consequences every time