Johns Hopkins experts weigh the risks and benefits of CT scans to detect lung cancer.
Lung cancer screening made headlines recently when The Early Lung Cancer Action Project (ELCAP) published new findings about spiral computed tomography (CT). This extremely sensitive imaging test detects lung cancer tumors under 1 cm in diameter. Traditional chest x-rays only detect lung cancer tumors 1-2 cm in size (stage I lung cancer tumors are defined as 3 cm or smaller). If lung cancer tumors are caught in the earliest stage, surgery can dramatically increase the odds of survival.
ELCAP examined spiral CT scans of 32,000 people at risk for lung cancer owing to a past or current smoking habit or exposure to secondhand smoke. Among participants, 484 people were diagnosed with lung cancer; 412 had stage I tumors. Researchers estimate that, after surgery, the stage I group had an 88% chance of living for 10 years.
Although these results sound like life-saving news, ELCAP was not a controlled study, meaning that spiral CT was not compared with other methods. Thus, researchers can’t say for certain that CT scans are better at diagnosing lung cancer and saving lives than chest x-rays or no screening at all -- an important consideration, since the scan is more expensive and exposes you to more radiation than traditional x-rays.
Most important, though, is the fact that spiral CT scans are so sensitive that they can detect abnormalities that may not be cancerous, such as scars or inflammation; the National Cancer Institute estimates that 25% to a whopping 60% of smokers have such lung abnormalities. In addition to causing needless worry, a false-positive result may lead to an unnecessary biopsy, which can be painful and put you at risk for infection or a collapsed lung.
The National Lung Screening Trial (NLST) will offer insight into these issues, including whether screening saves lives. Sponsored by the National Cancer Institute, NLST is comparing CT scans with chest x-rays among 50,000 current or former smokers. Final data won’t be available until 2009. In the meantime, spiral CT is an option for former smokers, but ask your doctor about your risk; it may be quite low depending on how long ago you quit. Therefore, the test’s drawbacks may outweigh any potential benefit.
This article comes from a recent issue of the Johns Hopkins Medical Letter: Health After 50. For more information about this acclaimed monthly newsletter, click here.
