ACS on lung cancer screening: Conversation, caution, then CT, maybe

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The American Cancer Society (ACS) has issued lung cancer screening guidelines and recommends clinicians discuss CT screening with patients who fit the profile of individuals screened in the National Lung Screening Trial (NLST). The ACS did not issue a blanket recommendation for screening, and instead stressed shared decision making and the critical role of high-volume, high-access screening centers.

The American College of Radiology (ACR) acknowledged the importance of the recommendation and has affirmed its plans to review evidence for creation of guidelines for CT lung cancer screening in spring 2014. In the interim, the ACR referred radiologists, healthcare providers and patients to the National Comprehensive Cancer Network (NCCN) guidelines.

The NCCN guidelines are prescriptive and contain specific and relevant information for radiologists, such as technical parameters for the low-dose CT exam and recommendations for follow-up exams, Ella A. Kazerooni, MD, director of cardiothoracic radiology at University of Michigan in Ann Arbor, told Health Imaging in an interview.

NLST showed a 20 percent reduction in lung cancer mortality among high-risk adults (current and former smokers ages 55 to 74-years old with at least a 30-pack-year history) who underwent three consecutive screening CT exams.

Several societies, including the American College of Chest Physicians, the American Society of Clinical Oncology and the American Lung Association, have issued guidelines recommending screening for individuals who fit NLST criteria. The NCCN guidelines expand screening to individuals 50 years or older with a 20-year pack history and one other known risk factor.

The ACS tempered its recommendation, and emphasized the need for clinicians to engage appropriate candidates in a discussion about the benefits, uncertainties and harms of screening prior to the decision to proceed with screening. Patients who undergo screening should be referred to experienced, organized programs that offer expertise in screening and access to a multidisciplinary team.   

“CT screening for lung cancer is a process, not a test performed in isolation,” Kazerooni wrote in Journal of the National Comprehensive Cancer Network in February 2012. She encouraged radiologists interested in involvement in lung cancer screening to build multidisciplinary collaborations with pulmonary medicine physicians and thoracic surgeons.

Screening: The fine print

How does screening CT support or counteract smoking cessation? A negative screen might provide smokers an excuse to continue the habit, or CT, coupled with counseling, may spur cessation. “Vigorous smoking cessation efforts must accompany [CT] screening for adults who are current smokers,” Richard Wender, MD, from Thomas Jefferson University Medical College, in Philadelphia, and colleagues wrote in the ACS guideline.  

The ACS focused on patient education and choice, and recommended providers share the following information with prospective screening candidates:

  • Lung cancer screening yields a relatively high rate of false positive results, with 39.1 percent of NLST participants experiencing at least one abnormal CT scan. Most findings are resolved with additional imaging.
  • Invasive procedures are possible, but not common, among patients with abnormal results.
  • CT screening and diagnostic evaluations expose patients to radiation, a risk that is not precisely quantifiable. However, the risk could lessen over time as CT scanners are updated and radiation dose criteria for screening are disseminated.
  • Incidental findings were reported in 7.5 percent of NLST participants, which may be a harm or benefit. The overall mortality reduction suggests a lack of harm associated with incidental findings, according to the ACS.
  • The ACS noted the prospect of overdiagnosis and explained the magnitude of overdiagnosis associated with lung cancer screening is unknown. “Based on the data from the NLST and PLCO [Prostate, Lung, Colorectal and Ovarian Screening Trial], some overdiagnosis is a possibility, but likely does not represent a significant fraction of the screen-detected cancers.”

The ACS emphasized the importance of an effective screening setting, noting that NLST sites met minimum equipment standards, adhered to a standard screening protocol and ensured radiologists and technologists had completed training in image acquisition and interpretation. "Whether community-based screening for lung cancer with low-dose CT will exceed or