Combined computed tomography (CT) and positron emission tomography (PET) - may detect the spread of head and neck cancer more accurately

Jul 26 2005

A highly powerful scanner combining two state-of-the-art technologies - computed tomography (CT) and positron emission tomography (PET) - may detect the spread of head and neck cancer more accurately than other widely used imaging examinations.

These findings, based on new research from the University of North Carolina at Chapel Hill School of Medicine, appear in the July issue of the medical journal The Laryngoscope.

The whole-body PET/CT also is highly accurate for detecting head and neck cancer recurrence, the researchers said.

"PET/CT is very helpful in determining where we should pinpoint our biopsies for recurrent disease," said Dr. Carol Shores, assistant professor of otolaryngology/head and neck surgery at UNC and the report's senior author. Shores is a member of the UNC Lineberger Comprehensive Cancer Center.

"We can pick up cancer where we thought none existed. The new scans are so precise that in some cases cancer had been detected that probably would not have been through any other noninvasive imaging exam."

Since its development in 2000, PET/CT imaging has enabled collection of both anatomical and biological information during a single examination. The PET component picks up the metabolic signal of actively growing cancer cells in the body, and the CT provides a detailed picture of the internal anatomy that reveals the size and shape of abnormal cancerous growths.

"Alone, each test has its limitations, but when the results of the scans are integrated they provide the most complete information on cancer location and metabolism," said Shores.

In cancer detection, the PET/CT has helped detect a variety of tumors, including cancers of the breast, esophagus, cervix, lung, colon and ovaries, as well as melanoma and lymphoma.

"Until now, no published study has specifically evaluated clinical outcomes with PET/CT for head and neck tumors, including its accuracy, use and implications for patient care," said Shores.

"In our review of nearly 100 patients at UNC, we wanted to find out where our best accuracy is in detecting these tumors with PET/CT." In PET/CT scanning, the patient lies on a table and is moved through the machine's doughnut-shaped tunnel twice, first to obtain the PET data and again for the CT.

Cancer cells require a great deal of sugar, or glucose, to have enough energy to grow. PET scanning uses a radioactive molecule similar to glucose called fluorodeoxyglucose (FDG), which accumulates within malignant cells because of their high rate of glucose metabolism. The patient receives an injection of this agent, and the whole-body scanner detects evidence of cancer that may have been overlooked or difficult to characterize by conventional CT, PET, X-ray or MRI.

In the new study, the PET/CT was shown to be 80 percent accurate for staging of distant metastasis, such as the spread of head and neck cancer to the lungs. This could affect the "intent of treatment," including decisions to preserve quality of life, Shores said.

Lung metastasis of head and neck cancer is not curable, Shores added. In these cases, patients receive palliative care rather than aggressive therapy, including major surgery or combined chemotherapy and radiation treatment. Such intensive treatments may cause difficulties swallowing and speaking, severe pain and other problems.

In addition to detecting distant metastasis, the study found the PET/CT more than 70 percent accurate in evaluating cancer recurrence. Future PET/CT studies at UNC will hone accuracy, Shores said. "We'll get more usable correct information because we now have a good idea of where we are most accurate."