LUNG CANCER SCREENING GUIDELINES

The US Preventive Services Task Force (USPSTF) has now issued its final recommendation on lung cancer screening, published December 31 in the Annals of Internal Medicine.

The USPSTF recommends annual screening for lung cancer with low-dose computed tomography (LDCT) for adults between the ages of 55 to 80 years who have a 30 pack-year smoking history and who currently smoke or have quit within the last 15 years.

In addition, they note that screening should be discontinued once a person has not smoked for 15 years or has developed a health condition that will substantially limit life expectancy or the ability or willingness to undergo curative lung surgery.

"It's clear that the longer and the more a person smokes, the greater their risk is for developing lung cancer," says the co-vice chair of the USPSTF Michael LeFevre, MD, MSPH, in a statement. "When clinicians are determining who would most benefit from screening, they need to look at a person's age, overall health, how much the person has smoked, and whether the person is still smoking or how many years it has been since the person quit."

The final recommendation follows closely the wording of the draft recommendation that the USPSTF issued July 2013, after which there was a time for comments. Both the draft and the final document concluded that there was a "moderate certainty" that annual screening is of "moderate net benefit" for individuals with a smoking history. This was a step forward from the recommendation it issued back in 2004, when it concluded there was insufficient evidence to recommend screening.

As previously reported by Medscape Medical News, this new recommendation is in line with those issued by several other bodies, including the American Cancer Society, the American College of Chest Physicians, and the National Comprehensive Cancer Network, which, in November 2011, was the first to issue a guideline for lung cancer screening.

Evidence and Harms

The USPSTF emphasizes that lung cancer screening is not an alternative to smoking cessation and that screening cannot prevent most deaths that are directly related to lung cancer. However, they found there was "adequate evidence that annual screening for lung cancer with LDCT in a defined population of high-risk persons" could prevent a substantial amount of disease-related mortality. The magnitude of individual benefit of screening also largely depends on a person's risk for developing lung cancer, as those facing the highest risk are the most likely to reap the benefits.

Harms have been associated with LDCT screening, including false-negative and false-positive results, incidental findings, overdiagnosis, and radiation exposure. A substantial proportion of individuals undergoing screening are affected by false-positives, notes the USPSTF, and the vast majority (95%) of all positive results do not lead to a cancer diagnosis. Although further imaging can resolve most false-positive results, some patients will undergo more invasive follow-up.

The USPSTF reports they found "insufficient evidence" on the harms associated with incidental findings, and although overdiagnosis of lung cancer does occur, the "precise magnitude is uncertain." The results of a modeling study that was conducted for the USPSTF estimated that 10% to 12% of screen-detected cancer cases are overdiagnosed.

Important Questions Remain

In an accompanying editorial, Frank C. Detterbeck, MD, from Yale University School of Medicine, New Haven, Connecticut, and Michael Unger, MD, from the Fox Chase Cancer Center, Philadelphia, Pennsylvania, emphasize that the USPSTF is recommending a structured and comprehensive screening process, and not just a scan.

However, this report does not address many of the practical aspects of implementing lung cancer screening, they say. For example, they note that "[D]isproportionate screening attracts individuals who have great anxiety about developing lung cancer even though their risk is actually not so high. These people need reassurance, with discussion of their risk for lung cancer and the issues associated with screening as they apply to them."

Another issue is patient selection and how it will actually occur in a real world setting, as "ample evidence shows underuse of cancer screening in populations for which it is indicated and overuse in those for which it is not," they write. "It is one thing to have strict criteria for entry into a study and no data that lung cancer screening works; it is another to argue that we should be screening and then expect that individuals with concerns can be excluded by simply drawing a line."

For a lung cancer screening program to be effective, it really needs to reach those at high risk, they comment. However, studies indicate that individuals at the highest risk seem less interested in being screened despite recognizing that they are at risk. The USPSTF also does not address who will evaluate people who are interested in or should consider CT screening for lung cancer, the editorialists write.

Many fundamental questions also remain, such as what the natural history of screen-detected cancer cases is, and are there criteria for whom and when to treat, Dr. Detterbeck and Dr. Unger point out.

"This is a dynamic field, and refinements in screening models could become available quickly," they write. "We should learn from differences among the randomized lung cancer screening trials.... If we stray too far from what we confidently know, we risk facing the difficult task of undoing mistakes. We need to implement screening given the evidence that we have, but we should proceed in a stepwise fashion."

Ann Intern Med. Published online December 31, 2013.