PET Not Ready for Routine Management of Head and Neck Cancer

NAPLES, Fla.-The use of positron emission tomography (PET) is not sensitive enough to warrant routine use in post-curative chemoradiation therapy diagnosis of patients with node-positive head and neck cancer, according to researchers in the field.

At least two recent studies have shown that after chemoradiotherapy, neck dissections indicate that as many as 38% of patients have residual cervical metastatic disease.

The use of computer-assisted tomography (CT) in evaluating patients following the node-positive neck after organ preservation therapy has been unreliable, said Victoria S. Brkovich, MD, a resident in the Department of Otolaryngology at the University of Texas Health Science Center at San Antonio.

In delivering the G. Slaughter Fitz-Hugh Resident Research Award here at the Southern Section Meeting of the Triological Society, Dr. Brkovich said that studies with CT show that the images have a sensitivity of 85%, specificity of 24%, and positive predictive value of 40%.

With those shortcomings in mind, some researchers have looked to PET imaging to predict residual cervical metastatic disease after treatment with chemoradiotherapy.

A significant number of head and neck squamous cell carcinoma with N2 or N3 disease harbor residual metastases despite an apparent clinical response. – -Christine Gourin, MD

Why Use PET to Detect Cancer

She explained that when patients are injected with the positron-emitting radionucleotide 18-fluorodeoxyglucose (FDG), the radionucleotide is taken up in cells by glucose transporters. Its distribution is a measure of glucose metabolism.

Because neoplasms generally demonstrate increased glucose metabolism, the uptake of 18-FDG PET may detect and localize a viable tumor.

In her study, Dr. Brkovich recruited 21 patients in a prospective case series in 2004 and 2005 who had undergone curative surgery and chemoradiation for squamous cell cancer of the head and neck. To be included in the study, patients had to have had biopsy-proven squamous cell carcinoma of the upper aerodigestive tract, node-positive neck disease, completion of the chemotherapy or chemoradiation protocol, a complete response at the tumor site, a post-treatment PET scan, and salvage neck dissection.

The sensitivity, specificity, and positive and negative predictive values were calculated based on the comparison of the PET scan result and the histopathological result of the corresponding neck dissection sample, she said.

Results Lacking Specificity, Sensitivity

The histopathological report found four neck dissections were positive for residual squamous cell carcinoma and the other 17 specimens were negative.

Dr. Brkovich said there were three true positive PET studies and one false negative PET study among the four specimen-positive findings. There were 11 true negative PET studies and 6 false positive PET studies.