USPSTF Finds 'Moderate Benefit' From Lung Cancer Screening

Zosia Chustecka

July 29, 2013

Annual screening for lung cancer in high-risk individuals is now recommended by the US Preventive Services Task Force (USPSTF) and many other professional organizations.

The USPSTF has issued a draft recommendation statement, which is it available for public comment until August 26.

The draft recommendation is based on a review of the evidence published online July 30 in the Annals of Internal Medicine. This review is also available on the USPSTF Web site, along with a modeling report.

The recommendation supports annual screening with low-dose CT for people deemed to be at high risk for lung cancer because of age and smoking history. This comprises current and former smokers 55 to 80 years of age with a smoking history of 30 pack-years or more who have smoked in the past 15 years.

According to the USPSTF, there is "moderate certainty" that annual screening is of "moderate benefit" for such people.

This recommendation updates the advice issued in 2004, when the USPSTF concluded that there was insufficient evidence to recommend screening.

The new recommendation is in line with that issued by several other bodies, including the American Cancer Society, the American College of Chest Physicians, and the National Comprehensive Cancer Network (NCCN), which, in November 2011, was the first to issue a guideline for lung cancer screening.

American Results Not Duplicated in Europe

Much of the evidence supporting lung cancer screening comes from the largest randomized trial of this intervention to date — the National Lung Screening Trial (NLST), which was conducted in the United States (N Engl J Med. 2011;365:395-409). The NLST involved more than 50,000 individuals but was stopped early after benefits were seen.

However, the USPSTF also considered evidence from smaller randomized trials conducted in Europe, which had different eligibility criteria from the NLST. Because those trials did not duplicate the findings of the NSLT, the USPSTF notes that "only moderate certainty exists about the magnitude of benefit from screening."

As a result, the recommendation for lung cancer screening is grade B; the highest ranking — grade A — means there is a "high certainty that the net benefit is substantial."

This is in contrast to the opinion issued by the NCCN, which "strongly recommended" lung cancer screening in high-risk individuals; that was a category 1 recommendation, which is based on high-level evidence (i.e., a randomized controlled trial) and uniform NCCN consensus that the intervention is appropriate.

"A category 1 recommendation is very uncommon," said Arnold J. Rotter, MD, from the City of Hope Hospital in Duarte, California, who was a member of the NCCN panel that wrote the guidelines. "The vast majority of clinical medicine wouldn't be considered category 1," he told Medscape Medical News. "Both mammography and colonoscopy — commonly performed cancer screenings — are only category 2A per the NCCN," he pointed out.

Balance of Benefit and Harm

The USPSTF estimates that lung cancer screening conducted according to its recommendations (i.e., annual screening for current or former smokers 55 to 80 years of age with a smoking history of 30 pack-years or more who have smoked in the past 15 years) would result in a 14% reduction in lung cancer mortality, or an estimated 521 lung cancer deaths prevented per 100,000 population.

However, the harms include an estimated overdiagnosis of 4% and radiation-induced lung cancer deaths of less than 1%.

There are other potential harms. The rate of false-negative results is estimated to range from 0% to 20%. Another problem is the rate of false-positive results; in the NLST, results were positive in less than 24.2% over 3 rounds of screening, but 96.4% of these were false-positive results. Also to be considered are incidental findings, the most common of which are emphysema and coronary artery calcifications, and potential psychological distress.

The USPSTF notes that the standard of care for lung cancer is surgery where possible, and radiotherapy and/or chemotherapy. So for individuals who are not suited for surgery because of comorbidities or poor functional status, screening might not be useful.

The recommendations also emphasize the importance of advising and helping people to stop smoking.

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