When the news that Peter Jennings had lung cancer was reported earlier this week, many WebMD users asked why doctors don't use chest X-rays to diagnose lung cancer at an early stage, when it's more treatable.

WebMD turned to cancer expert Harold Burstein, MD, assistant professor of medicine at Harvard Medical School in Boston, for the answer.

Lung Cancer Most Preventable

"Lung cancer is the No. 1 cause of cancer death in the U.S. for both men and women. The vast majority of lung cancer cases are caused by smoking," Burstein tells WebMD. "Thus, lung cancer simultaneously represents the most devastating cancer in our society, and the most preventable."

He says there are good screening tests for many types of cancer, such as Pap smear for cervical cancer, mammogram for breast cancer, and colonoscopy for colorectal cancer.

But what about chest X-rays for lung cancer?

Too Late for a Cure

"The answer is surprisingly complex," he says.

Chest X-rays are inadequate for diagnosing lung cancers at an early stage, when they are more treatable.

"By the time lung cancers are discovered on chest X-ray, the tumor is often too far advanced to allow the patient to be cured with surgery or radiation therapy. Chest X-rays often miss small, potentially curable lung tumors, as they are too hard to see," says Burstein.

In addition, many things seen on a chest X-ray turn out to be benign problems. "If you start getting lots of screening chest X-rays, you end up performing other testing on many patients, which are often unnecessary."

What About Spiral CT?

In recent years, a lot of attention has been paid to high-tech scans called high resolution, spiral CT scans. The hope was that these CT scans would be able to find smaller, earlier cancers without leading to further unnecessary tests.

"A variety of recent studies in the U.S. and Japan have suggested that high-resolution CT scans can often detect lung cancers. In particular, these cancers seem to be small (stage I), suggesting that they may be more likely to be cured with surgery," says Burstein.

However, he explains that these were small, early studies that were not able to answer the questions of whether CT scans can actually save lives.

Lung Cancer Screening Not Recommended

Burstein says that a recent analysis of potential lung cancer screening tests shows there is inadequate data to recommend widespread lung cancer screening at this time.

The report by the federal Agency for Healthcare Research and Quality and the U.S. Preventive Health Services Task Force says evidence that chest X-rays, CT scans, and other forms of screening can save lives is poor.

"In the case of lung cancer, prevention remains the best cure. If you care about someone, try to get them to stop smoking," Burstein says.

By Michael W. Smith, MD, reviewed by Charlotte E. Grayson, MD

SOURCE: Harold Burstein, MD, assistant professor of medicine at Harvard Medical School; medical oncologist, Breast Oncology Center, Dana-Farber Cancer Institute.