PET Imaging in Question

Ivanhoe Newswire
Wednesday, May 14, 2008; 4:15 AM

(Ivanhoe Newswire) -- The value of positron emission tomography with a radioactive tracer (FDG-PET) is in question after the results of a new study show it isn't effective in detecting small metastases in patients with head and neck cancer.

To form a prognosis for head and neck squamous cell cancers, doctors need to know if it has spread to nearby lymph nodes. While a patient may seem to be clinically clean, he may actually have small metastases. The standard testing includes using MRI (magnetic resonance imaging), CT (commuted tomography) and FDG-PET to detect small lesions.

Researchers from the University of Ioannina School of Medicine in Greece analyzed previously published studies that tested the performance of FDG-PET and found it failed to detect small lesions 50 percent of the time in node negative patients. It also misidentified normal tissue as being cancerous 13 percent of the time.

In addition, the researchers compared the sensitivity of FDG-PET with MRI and CT and found a trend for small improvement in detecting with FDG-PET, but nothing statistically significant.

The researchers concluded there was not enough evidence to support routine use of FDG-PET in patients with head and neck squamous cell cancer.

David L. Schwartz, M.D., a radiation oncologist at the University of Texas M.D. Anderson Cancer Center in Houston, and some of his colleagues disagree. In an accompanying editorial, they note the studies done so far have been single institutions and that no large randomized trials have looked at the issue. They also note clinicians rely on a variety of imaging techniques in addition to examinations. "Comparing one imaging technique against another may not adequately capture the possible benefit gained from an approach," the researchers wrote.

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SOURCE: Journal of the National Cancer Institute, published online May 13, 2008