Low-Dose CT Scans for Lung Cancer: A Bumpy Road to Solid Data and New Screening Guidelines

A Bumpy Start

On March 26, 2008, an article in the New York Times placed a promising test for lung cancer on shaky ground. The piece detailed that tobacco company money had paid for a 2006 groundbreaking study of the test, the results of which found that screening with low-dose computed tomography (CT) scans could greatly reduce the risk of dying from lung cancer. Until this time, no good screening test had been found for lung cancer – the most deadly cancer in the United States – and the study’s findings were met with cautious optimism in many scientific circles and wide praise in the broader media.

The results of the 2006 study – published in the New England Journal of Medicine – were impressive in their magnitude. They estimated that 80 percent of smokers screened with low-dose CT would survive for ten years, a percentage much higher than the average five-year survival rate of the disease.

Scientifically, the study had some issues (as we detailed in a post at that time). There was no comparison group, and the large long-term benefits of screening were projections based on only three years of follow-up, not on actual data from following patients over ten years. Despite this, the results showed potential for using low-dose CT to screen for lung cancer.

Then, the New York Times article came out detailing that not only had tobacco company money paid for the study but that it also funded a research foundation presided over by the principal investigator, who also happened to own pertinent patents in CT scanner technology. These revelations shook the scientific community, and the results of the study were called into question by many, with Dr. Catherine DeAngelis, then editor of the Journal of the American Medical Association, capturing the overall feeling: “I would never publish a paper dealing with lung cancer from a person who had taken money from a tobacco company.”

New Data. New Screening Guidelines

This could just be another story of tainted work quickly exiting into obscurity. Yet, the positive results for low-dose CT scanning for lung cancer have, somewhat surprisingly, largely been born out over time in more rigorous analyses, with the American Cancer Society releasing last week new lung cancer screening guidelines that focus on low-dose CT scans. Though benefits have been more modest than those in the 2006 study, a large randomized controlled trial (National Lung Screening Trail (NLST)) found that over an average of six years, current or former smokers screened with low-dose CT had a 20 percent lower risk of dying from lung cancer than those screened with standard chest X-rays.

These newer, more rigorous analyses, though, also highlighted the health risks that accompany the benefits of low-dose CT scans. While serious complications resulting from CT screening were rare in the NLST study, nearly 40 percent of patients receiving all three scheduled CT scans had at least one abnormal result requiring some sort of follow up. In comparison, just over 20 percent of women over age 40 who’ve had a mammogram report abnormal findings. And even though follow-up for an abnormal lung cancer screen most often involved just an additional CT scan, close to three percent of patients with abnormal scans had to have an invasive follow-up procedure, like biopsy or surgery.

“The risks of screening often get lost in the headlines,” says Graham Colditz, MD, DrPH, a Professor of Surgery at Washington University School of Medicine and Associate Director of Prevention and Control at the Siteman Cancer Center. “But they’re very important to consider, not only when forming guidelines but also in terms of someone’s personal preference for balancing the risks and benefits of having a screening test.”

The high percentage of abnormal scans with low-dose CT is a real concern, especially as this percentage will continue to grow as people continue to get scans. The large majority of these will be false alarms, but they can still be stressful and anxiety-inducing, as well as risky if follow-up needs to reach beyond additional scans to procedures like biopsies and surgery.

Who’s Likely to Benefit from Screening?

Despite such risks, the American Cancer Society’s new lung cancer screening guidelines detail who is most likely to benefit from screening with low-dose CT. This includes those between the ages of 55 and 74 who are relatively healthy current heavy smokers (1 or more packs a day for 30 years, for example) or former heavy smokers (those who quit less than 15 years ago). Screening should take place annually up to age 74 and in facilities or medical centers that have the experience and staffing to provide reliable scans, evaluation, and follow-up care. “If such a setting is not available and the patient is not willing or able to travel to such a setting,” the guidelines state, ” the risk of cancer screening may be substantially higher than the observed risks associated with screening in the NLST [study], and screening is not recommended.”

Quality and completeness of care is an important concern with CT screening, especially with such a high rate of abnormal results even in academic settings that are well staffed and trained in such scans. “It’s unclear how well these numbers will translate to broader medial care settings across the country,” says Colditz. “It’s a very specialized field. Outside of well-trained and well-staffed medical centers, the risks linked with screening could become much greater, and the benefits diminished. ”

The decision to get screened ultimately comes down to a personal decision. The guidelines state that screening is a decision that should be made along with one’s health care provider after weighing risks, benefits, and personal preferences. Those placing high priority on lowering the risk of dying from cancer who can also tolerate the uncertainty and anxiety of high rates of false alarms and follow-up procedures may choose annual screening. Those with lower tolerance for uncertainty of scan results may choose to not be screened regularly.

Benefits of Cessation

Whether or not someone chooses to be screened for lung cancer, the best thing any smoker can do for his or her health is to quit smoking, and the best thing any non-smoker can do is stay smoke free. Even given the significant benefits of low-dose CT scans, it doesn’t take long for the prevention benefits of cessation to surpass them, especially since smoking is linked to many other cancers as well as heart disease, stroke, and diabetes (figure).

The benefits of cessation match or exceed the known
benefits of low-dose CT screening for lung cancer.

“Smoking cessation is prevention,” says Melody Goodman, Assistant Professor in the Department of Surgery at Washington University School of Medicine. Whereas, “low-dose CT is a method of detection that helps find cancers early if they exist.” Screening and detection is very important, but preventing cancer outright, though cessation or other means, is always a top priority, continued Goodman.

Despite a rough start and some still unanswered questions about who exactly would benefit from low-dose CT screening, the addition of an effective screening test for lung cancer has great potential to reduce the burden of cancer in the United States. In 2009, over 200,000 people were diagnosed with lung cancer and close to 1600,000 people died from the disease. Any progress that helps lower these numbers – whether through screening, cessation, or both – will have a positive effect on individuals, on family and friends, and on the health system in general.

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