Concerns for Physicians About CT Lung Cancer Screening

By Steven Zinck, M.D, Thoracic Imaging Section Chief, The Radiology Group, P.C. at Providence St. Vincent Medical Center, and the Center for Medical Imaging

What we do know with certainty at this time about CT lung cancer screening is the following:

  • For those of you with patients in your practice who are interested this test, it should be limited to patients 50 years of age or older, with at least a 20 pack-year smoking history.
  • CT is much more sensitive than chest radiography for identifying lung nodules. It identifies smaller nodules and more of them.
  • Detecting smaller nodules presumably translates to identifying lung cancer at an earlier, more curable stage, but this may not be the case. Nodule size does not necessarily correspond to biologic aggressiveness.
  • CT screening identifies a higher percentage of Stage 1 lung cancers than chest radiography.

Other potential issues and concerns with CT screening include the following:

  • The risk of radiation from multiple CT scans is unknown, but these may increase the risk of other cancers. Even “low-dose” CT protocols deliver 10 times the radiation of a chest radiograph.
  • There is a high false-positive rate, which can be as high as 69% of people screened. This means many people with benign disease will need multiple follow-up scans, typically on a schedule of 3, 6, 12, and 24 months.
  • There is also a potentially unacceptably high false-negative rate.
    • Nagano trial, 32 of 88 cancers missed on initial screening (Li et al., 2002)
    • CT sensitivity for nodule detection = 50% (Rubin et al., 2005)
  • Morbidity, patient anxiety and cost of additional workup for positive scans may do more harm than good.
  • The cost of a national or international screening program may unduly burden the healthcare system.