Will lung cancer screening CT become standard of care for smokers?

Lung cancer screening CT took its most important step toward widespread implementation last week, when the U.S. Preventive Services Task Force (USPSTF) released a draft of its forthcoming recommendation that the 9 million U.S. people meeting entry criteria for the National Lung Screening Trial (age 55-79, with 30+ pack-years smoking history and quit < 15 years) should undergo yearly low-dose lung cancer screening CT.

The recommendation earned a Grade B in the USPSTF’s draft statement released July 29, 2013:

The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial.

Suggestion: Offer or provide this service.

The USPSTF’s recommendations have generally become the U.S. standard of care, both because of the authority of its expert panel, and because insurers face pressure to cover the recommended services. Under the Affordable Care Act (“Obamacare”), insurers are required by law to pay the entire cost of any screening service recommended by the USPSTF with a Grade A or B rating, without any copay or deductible.

The USPSTF did not recommend other screening methods like chest x-ray or sputum cytology. Previously the task force had either voted against lung cancer screening (in 1996) or declined to recommend either way, citing lack of evidence (2004).

systematic review in Annals of Internal Medicine was published simultaneously online as the basis of support for the USPSTF’s lung cancer screening recommendations.

Other advisory groups endorse lung cancer screening CT

The USPSTF’s recommendations follow those of the American Lung Association, American Cancer Society, and the American College of Chest Physicians and American Thoracic Society, all of whom have recommended lung cancer screening CT for people meeting the National Lung Screening Trial (NLST) entry criteria (but with varying degrees of strength).

The USPSTF made its own recommendation that screening should stop once a person reaches age 80.

However, they added the caveat that “caution should be used in recommending screening to patients with significant comorbidity, particularly those who are toward the upper end of the screening age range.”

In the National Lung Cancer Screening Trial, screening CT provided a 20% relative reduction in death from lung cancer, but 320 people had to be screened to prevent one lung cancer death. Total costs for a national program of lung cancer screening CT are estimated at $1.5 billion per year.

The USPSTF decided those numbers were well in line with other approved screening tests:

  • Mammograms: 1,905 women are screened to prevent one breast cancer death.
  • Flexible sigmoidoscopy: 871 screenings are needed to prevent one colon cancer death.

Most primary care physicians have not been recommending lung cancer screening CT, even to their high-risk patients, because the screening test has not been paid for by most insurance companies. Lung cancer screening CT costs about $300-400, although many hospitals have advertised steeply discounted lung cancer screening CTs in attempts to “capture” lucrative oncology patients.

Under the Affordable Care Act, insurance companies must pay in full for any screening test rated Grade A or B by USPSTF (i.e., no deductible or copay). To comply with current guidelines and to avoid liability from missed lung cancer diagnoses, primary care physicians will likely soon begin recommend lung cancer screening CT en masse.  Patients will have no financial disincentive to get their tests, and plenty of fear motivating them to do so.

Lung cancer screening CT holds promise, pitfalls

With 160,000 deaths from lung cancer in the U.S. alone, lung cancer screening CT is believed capable of preventing 12,000 deaths from lung cancer each year.

That’s expected to come with the cost of hundreds of thousands of false positives, as 40% of people in the NLST had at least one worrisome “positive” lung cancer screening CT. 95% of these proved to be false positives, but only after anxiety and a small number of biopsies and even surgeries, which these (cancer-free) patients would likely have avoided had they not been screened. These patients also received extra ionizing radiation from CTs, which carries about a 1 in 2,000 to 10,000 chance of causing cancer later. Low-dose screening CT may have a lower risk of causing cancer.

As many as 20% of patients in the NLST had false negative scans (they got lung cancer despite having had no detectable abnormality on their screening CTs).

Academics are busy parsing the NLST data to create lung cancer risk calculators and other schema to try to deploy lung cancer screening CT in the most effective way. Analysis of the NLST trial shows that most of the lung cancer risk was concentrated in 50-60% of patients; if they could be identified and screened more aggressively, lung cancer screening CT might sooner achieve its potential for saving thousands of lives from this lethal disease.

Matthew Hoffman is a pulmonary and critical care physician who blogs at PulmCCM.org.

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