Recent years have seen the release of controversial recommendations regarding screening for breast and prostate cancer. Now, the topic of cancer detection is back in the news with the American Cancer Society’s (ACS) announcement of new guidelines for lung cancer screening; the guidelines recommend annual low-dose computed tomography (LDCT) for high-risk individuals, with the goal of reducing lung cancer mortality. The chief ACS recommendation is that clinicians should encourage annual LDCT screening for individuals between the ages of 55 and 74 years who have at least a 30-pack-year smoking history, currently smoke, or have quit smoking within the past 15 years, and are in relatively good health.
The new guidelines are primarily based on the results of the National Cancer Institute’s National Lung Screening Trial (NLST), a prospective study that randomized more than 50,000 persons age 55 to 74 years with an extensive smoking history to three annual screenings with LDCT or chest x-ray (CXR). After a median follow-up of 6.5 years, LDCT was associated with a 20.3% reduction in lung cancer mortality and a 6.9% reduction in overall mortality compared with CXR. In the LDCT group, 24.2% of 75,136 screenings were positive, resulting in the diagnosis of 649 lung cancers, whereas in the CXR group, 6.9% of 73,499 screenings were positive, leading to the diagnosis of 279 lung cancers.
The authors of the ACS recommendations acknowledge the risks associated with regular screening. Almost 40% of subjects in the LDCT arm of the NLST received positive results on at least one screen, but only 3.6% of the positive screens actually detected a tumor. False-positive tests are not necessarily harmless, as they may result in anxiety, additional imaging tests, and biopsy procedures for the patient. However, only 2.7% of subjects who had false-positive results underwent an invasive procedure, and few subjects with benign abnormalities who underwent additional testing experienced complications, so the risk of harm appears to be low.
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Frequent screening also carries a risk for radiation exposure, which prompted a recommendation in the ACS guidelines to reserve screening for persons who are at high risk; for individuals at lower-risk, the harm from radiation might exceed the benefit from early detection of lung cancer.
Discovery of incidental findings is a potential benefit—and a potential harm—of annual screening for lung cancer. In some cases, detecting cardiac, vascular, or other abnormalities might be very much in the patient’s interest, whereas in others, anxiety and additional unnecessary testing might be the only outcome. The ACS authors concluded that, since all-cause mortality was lower in the LDCT group, such potential harms did not outweigh the benefits.
The ACS recommends that, in conversations with patients, clinicians address these issues:
- Screening with LDCT has been shown to reduce the risk of dying from lung cancer.
- LDCT will not detect all lung cancers or all lung cancers early; some patients who have a lung cancer diagnosed by LDCT will still die from the disease.
- False-positive results may occur, leading to recommendations for additional testing or invasive procedures, which may carry risks of complications.
- The opportunity to detect lung cancer early does not diminish the importance of smoking cessation.
- Most government and private insurance plans will not pay for annual LDCT screening, and patients must be made aware that they may be responsible for the costs.
- Screening should take place at an institution with expertise in LDCT.
Lung cancer is the leading cause of death from cancer in the United States and accounts for more than one-fourth of all cancer deaths. The average 5-year survival for persons with lung cancer is 16.8%, among the lowest of all cancers.
