CMS Proviso on Lung Cancer Screening: Good or Bad?

H. Jack West, MD

Disclosures

December 11, 2014

'Potential Barriers or Appropriate Guardrails'?

On November 10, the Centers for Medicare & Medicaid Services (CMS) proposed a decision to cover low-dose chest computed tomography (LDCT) screening for lung cancer in high-risk patients, provided that the screening is done at specific, experienced screening facilities and is preceded by careful counseling and shared decision-making about the benefit vs risk of screening for each patient.[1] The imposed limitations may be viewed either as unprecedented potential barriers to screening or as appropriate guardrails to ensure that LDCT screening is done as well as possible. It's worth reviewing the key issues enumerated by CMS, which highlight that screening which is poorly understood by patients or poorly conducted by centers with insufficient infrastructure and experience may well cause harm rather than benefit.

The population considered eligible for screening mimics the one studied in the National Lung Screening Trial (NLST)[2] that enrolled 53,454 patients and demonstrated a 20% improvement in survival among screened patients—specifically, patients ranging in age from 55 to 74 years, without symptoms of lung disease, with a smoking history of at least 30 pack-years, and who are either current smokers or had quit smoking in the past 15 years.

Although there are certainly patients outside of these parameters who would be missed by LDCT screening, it is important to recognize that in the NLST, over 95% of nodules detected were benign. More notably, in an analysis of results as a function of risk level among the patients enrolled on NLST, divided into quintiles, the patients who were eligible and in the highest risk quintile detected 65 false-positive nodules and needed to screen 161 patients for each life saved from lung cancer; in contrast, in the lowest risk tier, 1648 false-positive nodules were detected, and over 5000 patients needed to be screened per life saved from lung cancer.[3] Clearly, this work illustrates the importance of risk for lung cancer in the balance of probability of false-positive vs true-positive results in LDCT screening, and underscores why it would be inappropriate to generalize survival benefit found in higher-risk older patients to younger patients with a less extensive smoking history.

Shared Decision-Making, Counseling, and Quality Control

A second key component of the screening requirement posed by CMS is that screening centers must include shared decision-making and careful counseling. It is important for patients to understand the high probability of detecting one or more nodules that may lead to a recommendation for further surveillance imaging, or potentially interventions, but that are unlikely to represent actual cancer. At the same time, patients must understand that screening will not detect all lung cancers in time to provide curative therapy. Counseling services are mandated to also include smoking cessation or discussion of the value of ongoing abstention from tobacco, because some patients may potentially see a negative CT scan as an exoneration and license to continue to smoke. In fact, one model of LDCT screening found that the efficacy of smoking cessation counseling during the screening process had a remarkable impact on the cost-effectiveness of lung cancer screening.[4]

A final component of the CMS recommendation for LDCT screening is aimed at quality control for centers and the screening process. Eligible centers for LDCT screening must have participated in prior screening trials and administer scans with an effective radiation dose of less than 1.5 mSv, which is under 20% of the radiation dose of a standard diagnostic CT[5] and also less than half of estimated annual environmental exposure.[6] These approved centers must also collect and submit data to a national registry on results of screening studies performed, so that CMS can gather information on the efficacy of LDCT screening efforts in the real-world setting. Given the uncertainty about cost and benefit vs risk of screening, these registry data will be extremely instructive.

Important Not to Set the Bar Too Low

Taken together, these requirements may be viewed as a barrier that could limit screening, but all testing engenders a balance between sensitivity and specificity. Given the financial burden and risks of false-positive detection of benign nodules that lead to patient anxiety, additional imaging, and very possibly invasive testing, it is necessary to be careful about not setting the bar for screening too low. At the same time, delineating specific requirements for scanning and interpretation quality for LDCT imaging, as well as specific expectations for shared decision-making and counseling for potential screening candidates, ensure that patients understand the balance of anticipated benefit vs risk of screening and maximize the benefit of the "teachable moment" of lung cancer screening for smoking cessation. Finally, having participating centers contribute data to a central registry enables CMS to clarify the cost-effectiveness and false vs true positivity rates of LDCT screening in actual practice. It is important for us to recognize the high stakes and potential harm in lung cancer screening, particularly if not done well; CMS is appropriately framing its decision as a means of optimizing its implementation.

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