Positron emission tomography using [¹⁸F]fluorodeoxyglucose (FDG-PET) in the clinically negative neck: is it likely to be superior?

The capability of modern imaging techniques such as CT, MRI, US and US-guided fine-needle aspiration cytology (USgFNAC) to detect small tumour deposits is limited. Therefore, the detection of occult metastases in the clinically negative neck remains a diagnostic problem. One of the novel options to refine staging of head and neck cancer is [¹⁸F]fluorodeoxyglucose positron emission tomography (FDG-PET). To evaluate the diagnostic value of FDG-PET in the detection of occult malignant lymph nodes, we compared the results of FDG-PET with other diagnostic techniques and the histopathological outcome of 15 neck dissection specimens from 15 head and neck cancer patients with a clinically negative neck. Three sides contained metastases of squamous cell carcinoma. FDG-PET enabled detection of metastases in two sides, which were also detected by MRI or USgFNAC. FDG-PET and CT missed metastases in one patient, which were detected by both MRI and USgFNAC. In studies with a detailed examination of lymph nodes of a neck dissection, a low sensitivity of FDG-PET for the detection of occult lymph node metastases is found. It is unlikely that FDG-PET is superior in the detection of occult lymph node metastases in head and neck cancer patients with a palpably negative neck. The histopathological method used seems to be the most important factor for the differences in sensitivity in reported FDG-PET studies. New approaches such as the use of monoclonal antibodies labelled with a positron emitter may improve the results of PET in these patients.