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Task force recommends annual low-dose CT screening for those at high risk of lung cancer

August 14, 2013
Dr. Bernardo Goulart in the Fred Hutch Public Health Sciences Division is a medical oncologist who specializes in caring for patients with lung cancer and head and neck cancers.

Dr. Bernardo Goulart in the Public Health Sciences Division at Fred Hutch is a medical oncologist who specializes in caring for patients with lung cancer and head and neck cancers.

By Andy Koopmans

The U.S. Preventive Services Task Force recently issued a draft statement on lung cancer screening that came out in favor of annual screening with low-dose CT (computed tomography) scans for those at high risk based on age and smoking history. Low-dose CT uses X-rays to take high-resolution pictures of the lungs, which allows physicians to detect any abnormal spots on the lungs, many of which are too small to see on a standard X-ray. Low-dose scans usually administer between one-fifth and one-half less radiation than a standard X-ray.

This new draft statement is a revision of the Task force’s original 2004 recommendation, which did not advocate for such screening.

The change is prompted by the results of the National Lung Screening Trial , a randomized, controlled trial by the National Cancer Institute involving more than 53,000 asymptomatic individuals considered at high risk for lung cancer due to their age and smoking history. In that study, individuals were randomly assigned to receive screening with low-dose CT versus chest X-ray for three consecutive years and then underwent follow-up a median of six-and-a-half years later. The trial showed a 20 percent relative reduction in lung cancer death in those who underwent low-dose CT and a 7 percent relative reduction in overall mortality.

“This was an anxiously awaited decision to which most screening investigators would agree,” said Dr. Bernardo Goulart, an affiliate investigator in the Public Health Sciences Division of Fred Hutchinson Cancer Research Center and part of the Hutchinson Institute for Cancer Outcomes Research team at Fred Hutch. “Without screening, most patients present with either locally advanced or advanced stages of the disease and these are usually incurable or carry low probabilities of cure with standard treatments,” he said. “With low-dose CT screening, we will be able to detect cancers at early stages and provide patients with a higher chance of cure with surgery. We welcome the decision of the U.S. Preventive Services Task force because well-implemented screening may avoid 18,000 lung cancer deaths every year.”

The recommendations are for annual screenings of current and former smokers who’ve quit within the past 15 years, are 55-79 years old and have a 30-pack-year history. A “pack year” is equivalent to smoking an average of a pack a day for a year. The age recommendation exceeds the range of the National Lung Screening Trial, a fact that surprised Goulart.

“The recommendation is remarkable because the Task force has usually taken a conservative approach as far as cancer screening recommendations, most notably the recommendation to restrict breast cancer screening to 50 years and over and more recently their recommendation against routine prostate cancer screening with PSAs (biochemical markers),” he said. “The reason prompting the more generous age range for lung cancer screening comes from a decision model study—a study that projected the benefits of screening at the population level based on multiple sources of data, including the NLST—which determined that screening up to age 79 would lead to more lives saved.”

Potential harm
Low-dose CT screening is not without risks. The Task force found that lung cancer screening has some harms, including false-positive results, which can cause anxiety and worry and can lead to follow-up tests and procedures that aren’t needed and may have their own risks. Additionally, although radiation exposure from such screening is five times lower than the amount involved in a chest X-ray, repeated scans may cause cancer in otherwise healthy people.

However, the net benefit of low-dose CT appears to outweigh the risk, Goulart said. “There is approximately one radiation-induced cancer case per 2,500 individuals screened, which compares favorably to 320 individual screenings to avoid one cancer death. The net benefits favor screening, but a small risk of radiation exists. We really don’t have a clear sense of what that risk is because we need more time from the NLST study to see the outcomes.”

Cost effectiveness
The results of the National Lung Screening Trial sparked debate among health care providers and policymakers about the practical logistics and economic implications of the screening recommendations. “Their recommendations left some areas of uncertainty unaddressed regarding lung cancer screening, specifically in that they didn’t comment on the economic impacts of implementing low-dose screening on a large scale,” Goulart said. “We have done cost studies using budget-impact models that predict a high national health care cost of screening if we implement it to a broader eligible U.S. individuals—up to $3.3 billion a year just on screening expenditures. We know other cost-effectivness analyses have been published, but they really do not answer the question of whether low-dose CT is cost effective due to multiple methodological problems, most notably that the most recent cost-effectiveness analyses have all been based on observational studies, not randomized trials. The Task force should have made some comments on the economic impact of such screening.”

Goulart and HICOR Director Dr. Scott D. Ramsey, a health care economist and internist in the Fred Hutch Public Health Sciences Division, further describe implementation strategies that ensure eligible patients derive benefits of screening while avoiding unnecessary use of test procedures in a paper published online last month in The Oncologist.

About lung cancer

Lung cancer is the third most common cancer in men and women and ranks first in the number of cancer-related deaths in the United States. The most important risk factor for lung cancer is smoking, which results in approximately 85 percent of all lung cancer cases in the U.S., and the incidence increases with age, most commonly occurring in people age 55 and older.

About 85 percent of lung cancer patients die from the disease, in part because it is often not found until the cancer is at an advanced stage. However, the most common type, non-small-cell lung cancer, if detected early can be treated surgically and has a better prognosis.

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