Detecting Spread of Non–Small-Cell Lung Cancer within the Chest

What is the problem and what is known about it so far?

In the United States, lung cancer is the second most common cancer in both men and women. The most common type of lung cancer is non–small-cell lung cancer. Lung cancer occurs when abnormal cells in the lung divide without control. Sometimes the cancer cells invade nearby tissue and spread through the blood and lymph system to other parts of the body. Some of the first places that lung cancer cells invade are lymph nodes in the area between the lungs (mediastinum).

Doctors usually use scans, such as computed tomography (CT) scans or positron emission tomography (PET) scans, to see whether lung cancer has spread to mediastinal lymph nodes. A computer linked to an x-ray machine creates CT scans. These scans give a series of detailed pictures of body structures. The PET scan is a relatively new test that involves injecting a radioactive substance into a vein. Cancer cells take up and trap the substance more than do normal cells. The PET scan gives pictures of areas of the body that are “lit up” because cells in that area are rapidly trapping the radioactive substance. There are many studies that look at the ability of CT and PET scans to detect the spread of lung cancer to mediastinal lymph nodes.

Why did the researchers do this particular study?

To compare the accuracy of CT and PET scans for detecting spread of non–small-cell lung cancer to mediastinal lymph nodes.

Who was studied?

More than 2500 patients who had participated in 39 different studies.

How was the study done?

Rather than doing a new study, researchers looked at past studies that assessed the accuracy of PET or compared the accuracy of PET with CT for diagnosing spread of cancer to lymph nodes. All patients in the studies had non–small-cell lung cancer. Most patients had biopsies to definitively diagnose spread of cancer to mediastinal lymph nodes. The researchers summarized data from the different studies to see whether CT or PET was better in detecting nodes that did and did not show cancer.

What did the researchers find?

Positron emission tomography was more accurate than CT for identifying cancer spread to lymph nodes. Also, both true-positive and false-positive PET findings were more common in people with enlarged lymph nodes than in people with normal-sized lymph nodes.

What were the limitations of the study?

The study only assessed the ability of PET and CT to detect spread of cancer to mediastinal lymph nodes. Because PET and CT sometimes find spread of cancer in other parts or structures of the body, all of the potential benefits of the 2 tests weren't studied.

What are the implications of the study?

Positron emission tomography is more accurate than CT for mediastinal staging of non–small-cell lung cancer. Because PET has more false-positive findings in patients with enlarged nodes, positive findings need biopsy confirmation.