Prediction of ultrasound guided fine needle aspiration cytology results by FDG PET-CT for lymph node metastases in head and neck squamous cell carcinoma patients

Abstract

Introduction: Accurate assessment of cervical lymph node status is essential in patients with head and neck squamous cell carcinoma (HNSCC) as it influences prognosis and treatment decisions. During patient workup, lymph node status is often examined by ultrasound guided fine needle aspiration cytology (USgFNAC). 18F-Fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG PET-CT) is frequently used to assess primary tumor and distant metastases but provides information on lymph node status as well. It is possible that FDG PET-CT (if already made for abovementioned indications) can predict the results of USgFNAC in subgroups of lymph nodes based on FDG-uptake and size. The objective of this study is to identify maximum standardized uptake (SUVmax) and short axis diameter cutoff values of lymph nodes at which FDG PET-CT can reliably predict USgFNAC results. Methods: One hundred and seventeen patients with HNSCC were retrospectively analyzed. Patients were included when FDG PET-CT and USgFNAC were available. SUVmax measurements were performed and compared to the USgFNAC results. Results: Using USgFNAC as a reference standard, the area under the curve of the receiver operating curve was 0.91. At an SUVmax cutoff value of 4.9, the accuracy of FDG PET-CT was the highest (85%). Lymph nodes with short axis diameter ≥1.0 cm and SUVmax ≥4.9 were in 91% positive on USgFNAC. If SUVmax was below 2.2, no nodes were positive on USgFNAC. Of all lymph nodes 52% either had a short axis diameter ≥1.0 cm and SUVmax ≥4.9 or an SUVmax <2.2. FDG PET-CT and USgFNAC results were very similar in these nodes. Conclusions: By measuring SUVmax values and minimal axial diameters of lymph nodes and using appropriate cutoff values, FDG PET-CT can predict the results of USgFNAC examinations in half of the examined lymph nodes. This information may lead to a reduction of USgFNAC examinations in HNSCC patients if FDG PET-CT is already performed for other indications.