A thorax and lung computed tomography image. (iStock)

The warnings are old hat by now: According to the Centers for Disease Control and Prevention, smoking causes about 1 in 5 deaths in the United States each year. Despite nationwide decreases in smoking over the decades, lighting up remains the country’s leading cause of preventable disease.

Luckily, writes Indiana University medical professor Richard Gunderman, there’s a test that can save smokers’ lives, even among those who have been on cigarettes for years. It’s CT lung cancer screening, and Gunderman makes a case for the tool at the Conversation, a not-for-profit media outlet.

In CT lung cancer screening, a low-dose X-ray machine scans patients’ lungs. The images that result can help pinpoint the telltale signs of cancer. The U.S. Preventive Services Task Force recommends that people with a history of heavy smoking who smoke now or have quit within the past 15 years and who are between ages 55 and 80 get the screening yearly.

But too few take advantage of the test, Gunderman writes. “Many patients and even some physicians simply don’t know about the test, and even patients who do may decline to undergo it,” he writes.

Gunderman makes a compelling argument about why the technique should be better known — and what early detection can do for those who do have lung cancer. Though false positives do occur in some cases, that risk is outweighed by the potential benefit of the test for qualified patients. Lung cancer symptoms, such as coughing up blood, only occur once cancer is advanced, Gunderman writes. In contrast, CT scans can detect lung cancers in their early stages.

For some lifelong smokers, warnings to quit can seem as stale as old cigarette smoke. CT lung cancer screening can’t undo the effects of smoking, but it can detect lung cancer before it’s too late to treat. Read Gunderman’s case for the screening at bit.ly/CTlung