Risk Variation: Lung Cancer Screening and the United States Preventive Services Task Force

Reprinted from the Pathways, Spring 2014. Pathways is LCRF’s Semi-Annual Newsletter.

by Peter B. Bach, MD, MAPP
Memorial Sloan-Kettering Cancer Center, New York, NY

In November 2010, the National Lung Screening Trial (NLST) announced results which identified a 20% relative reduction in lung cancer mortality from screening for lung cancer with low-dose computed tomography (LDCT) compared to Chest radiograph. These results, from a large and well-designed randomized controlled trial (RCT), prompted professional societies to advocate the use of LDCT screening in high risk populations. (1-4) Late last year the United States Preventive Services Task Force (USPSTF) added to this growing body of recommendations. (5)

The USPSTF is an independent group of experts funded and appointed by the federal government which evaluates preventive services. Since 2008 Medicare has been able to cover new preventive services that receive A or B grades from the USPSTF. In 2010, the Affordable Care Act (ACA) mandated the coverage of USPSTF A or B graded services by most private insurance plans and removed coinsurance for Medicare covered services. (6) In light of this expanded role, the processes used by the Task Force to develop their recommendations are of increased importance.

The USPSTF bases its grading system on a service’s expected net benefit and the certainty of that benefit. A potential weakness of this strategy is that it treats the net benefit determination as constant throughout the population. Even within the NLST eligible population there is a wide range of expected net-benefit from LDCT screening. A recent study has suggested that the number of false positive results per prevented lung cancer death (a measure of net-benefit) from LDCT screening varied 25-fold between low and high risk NLST participants. (7) A more nuanced set of recommendations would assign different grades to these high and low risk individuals.

Following several guidelines released by professional societies, the USPSTF also recommended screening for a group not studied in the NLST, 75-80 year olds with a substantial smoking history. The USPSTF relied on disease state models to provide evidence for this recommendation, extrapolating the NLST results to older individuals. Such extrapolation is considered to be lower quality evidence than RCTs or observational studies, implying that the certainty of the net benefit in this population is also lower. Ideally the grading of the recommendation to screen 75-80 year olds would reflect this.

There is strong evidence that LDCT screening for lung cancer is beneficial for individuals at high risk of developing the disease. However, this benefit will vary significantly from person to person. Despite largely following previous guidelines, the USPSTF’s recommendation lacks the parsimony necessary to communicate this critical point.

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References

1. Bach PB, Mirkin JN, Oliver TK, Azzoli CG, Berry DA, Brawley OW, et al. Benefits and harms of CT screening for lung cancer: a systematic review. JAMA. 2012;307(22):2418-29.
2. Jaklitsch MT, Jacobson FL, Austin JH, Field JK, Jett JR, Keshavjee S, et al. The American Association for Thoracic Surgery guidelines for lung cancer screening using low-dose computed tomography scans for lung cancer survivors and other high-risk groups. J Thorac Cardiovasc Surg. 2012;144(1):33-8.
3. Wender R, Fontham ET, Barrera E, Jr., Colditz GA, Church TR, Ettinger DS, et al. American Cancer Society lung cancer screening guidelines. CA Cancer J Clin. 2013;63(2):107-17.
4. Wood DE, Eapen GA, Ettinger DS, Hou L, Jackman D, Kazerooni E, et al. Lung cancer screening. J Natl Compr Canc Netw. 2012;10(2):240-65.
5. Moyer VA. Screening for Lung Cancer: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2013.
6. Bach PB. Raising the Bar for the U.S. Preventive Services Task Force. Ann Intern Med. 2013.
7. Kovalchik SA, Tammemagi M, Berg CD, Caporaso NE, Riley TL, Korch M, et al. Targeting of low-dose CT screening according to the risk of lung-cancer death. N Engl J Med. 2013;369(3):245-54.