Task Force Recommends Annual Screening for Lung Cancer in High-Risk Populations
The US Preventive Services Task Force (USPSTF) is recommending that individuals aged >55 years who have a history of heavy smoking be screened annually for lung cancer.
If adopted, this initiative will bring an estimated 14% reduction in lung cancer–related mortality as a result of early disease detection, according to the USPSTF position paper, which was recently published online (Moyer VA. Ann Intern Med. 2014 January 14. Epub ahead of print).
“It’s clear that the longer and the more a person smokes, the greater their risk is for developing lung cancer,” stated the task force’s co–vice chair Michael L. LeFevre, MD, MSPH, Vice Chair, Family and Community Medicine, University of Missouri, Columbia. “When clinicians are determining who would most benefit from screening, they need to look at a person’s age, overall health, how much the person has smoked, and whether the person is still smoking or how many years it has been since the person quit.”
The task force further suggests that screening be discontinued once a person has not smoked for 15 years or lacks the ability (because of medical reasons) or the willingness to have curative lung cancer surgery.
Currently, lung cancer is the leading cause of cancer-related death in the United States, with high rates of mortality that are attributed to the late stage at which most cases are diagnosed—early detection of the disease is uncommon because of its largely asymptomatic progression.
Because of the later-stage diagnoses, the typical patient with lung cancer has an abysmal 5-year survival rate of 17%. Rates are much higher (52%) when the disease is detected early; however, only 15% of lung cancer cases are diagnosed early.
New Data, Updated Recommendations
The current recommendations take into account new data that bolster the case for widespread screening programs and that validate low-dose computed tomography (LDCT) as the screening method of choice.
Most of the information used to form the USPSTF’s opinion came from 2 sources: the National Lung Screening Trial (NLST)—the largest such trial ever performed—and a modeling study performed by the Cancer Intervention and Surveillance Modeling Network, as commissioned by the USPSTF.
In the NLST trial, 53,454 individuals aged 55 to 74 years who were current or former smokers (quit within the past 15 years) and had a 30–pack-year smoking history were screened 3 times annually with LDCT or standard chest x-ray.
After a median follow-up of 6.5 years, participants receiving low-dose helical CT scans had a 20% lower risk of dying from lung cancer than participants who received standard chest x-rays; this translated into an LDCT tumor sensitivity of 93.8% and a specificity of 73.4%.
Using these data, as well as data from smaller randomized trials of lung cancer screening, the USPSTF arrived at its current recommendations of screening 30–pack-year smokers aged 55 to 80 years (older than the NLST cohort) once annually, with the preferred method of LDCT.
That said, the USPSTF report is chock full of caveats, many of which power the argument against screening younger and/or less-frequent smokers. Those caveats, in descending order of concern, are:
- False findings. In the NLST, 24.2% of screening test results were positive; 96.4% of these results were false-positives. Most false findings were invalidated by repeat imaging; however, roughly 2.5% of positive test results required additional invasive diagnostic procedures (ie, needle biopsy). Of 17,053 positive test results that were evaluated, additional tests resulted in 61 complications and 6 deaths
- Overdiagnosis. Results from modeling studies suggest that up to 12% of actual cancer cases identified by screening would not have otherwise been detected in the patient’s lifetime, meaning that these slow-growing tumors posed less threat to the patient than the screening itself
- Radiation exposure. LDCT studies incur approximately 1.5 mSv of radiation per scan—this is less than typical annual background radiation, but more than a standard mammography (ie, 0.7 mSv). The USPSTF considers the risk from radiation at this level to be negligible
- Inadequate expertise. Although difficult to quantify, the USPSTF panel members acknowledged that the conditions of the NLST screen may not be easily replicated in the community setting. Therefore, the panel recommends that quality standards for LDCT, as well as protocols for related follow-up for positive results, be established.
Cost of Screening
Strikingly, the USPSTF recommendations mention nothing about cost beyond suggesting that smoking cessation programs are cheaper. However, a recent article published in a journal of the H. Lee Moffitt Cancer Center (Nanavaty P et al. Cancer Control. 2014;21:9-14) addressed this issue.
In the Moffitt analysis, assuming an average cost of $300 per LDCT screen, and using outcomes from the NLST, lung cancer screening incurs costs of $126,000 to $169,000 per quality-adjusted life-year (QALY) for patients with a 20–pack-year habit, and $110,000 to $166,000 per QALY for a 40–pack-year individual.
By contrast, mammography was equal to $47,000 per QALY. (Although the cost-effectiveness ratios for the NLST are not yet available, some reports have estimated costs at $38,000 per QALY.)
Of note, should these recommendations be adopted, effective prevention measures are covered under the Affordable Care Act without copayments or other barriers starting January 1, 2015.