Positron emission tomography with a radioactive tracer (18F-FDG PET) may not improve the detection of small metastases in patients with head and neck cancer who have no clinical evidence of disease in neighboring lymph nodes, according to a meta-analysis published online May 13 in the Journal of the National Cancer Institute.
A key prognostic factor for head and neck squamous cell cancer patients is whether their disease has spread to the nearby lymph nodes. Unfortunately, some patients who appear clinically to be free of such metastases, referred to as cN0, actually have small metastases. Clinicians use magnetic resonance imaging (MRI), commuted tomography (CT), and FDG-PET to try to detect these lesions, but strong data supporting the use of FDG-PET are lacking.
To systematically examine the value of FDG-PET for diagnosing clinically node-negative patients, John P. A. Ioannidis, M.D., of the University of Ioannina School of Medicine in Greece and colleagues performed a meta-analysis of 32 previously published studies that tested FDG-PET in head and neck cancer patients with one or fewer nodal metastases.
FDG-PET failed to identify 50 percent of the occult lesions in clinically node-negative patients and incorrectly identified normal tissue as being cancerous 13 percent of the time. When the researchers compared the sensitivity and specificity of FDG-PET with MRI and CT, they found that there was a trend for a small improvement in detection with FDG-PET, but the differences were not statistically significant. The false positive rate was similar for all three imaging techniques.
"Thus, there is little evidence to support the routine use of 18F-FDG-PET to evaluate possible lymph node metastasis among patients with [head and neck squamous cell cancer] and a clinically negative neck," the authors write.
In an accompanying editorial, David L. Schwartz, M.D., of the University of Texas M. D. Anderson Cancer Center in Houston and colleagues commend the authors for their efforts to systematically analyze the value of FDG-PET in diagnosing clinically node-negative head and neck cancer patients. They note that single institutions studies have provided most data thus far, as no large randomized trials have addressed the question.
The editorialists contend, however, that clinicians typically use one or more diagnostic imaging techniques, as well as clinical examinations, to assemble an overall picture of their patient's disease and do not rely on a single test. Therefore, comparing one imaging technique against another may not adequately capture the possible benefit gained from an approach. "Prospective data remain a critical necessity to translate imaging improvements with FDG-PET into proven treatment improvements," the editorialists write.
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