18F-fluoro-L-thymidine Positron Emission Tomography for Mucosal Head and Neck Squamous Cell Carcinoma Treated with Definitive Chemoradiation: A Pilot Study of Nodal Assessment and Tracer Safety

Abstract

We aim to assess the utility and safety of 18F-fluoro-L-thymidine- positron emission tomography (FLT-PET), in reference to 18F-2-fluoro-2-deoxy-D-glucose (FDG-PET) in the assessment of nodal involvement for mucosal head and neck SCC (HNSCC). Methods. Ten patients with HNSCC receiving definitive chemoradiation (CRT) were enrolled. Baseline FLT-PET and FDG-PET were obtained. The total number of involved lymph nodes and ultimate nodal staging by the baseline FDG-PET and FLT-PET was compared. Receiver Operating Characteristics (ROC) analysis for the matched nodes was performed to identify an optimal maximal standardized uptake value (SUVmax) cutpoint. Results. The tracer uptake by the involved nodes on FDG-PET was higher than those judged to be involved by FLT-PET (mean SUVmax: 5.9 versus 3.4; P<0.001). More abnormal lymph nodes were detected by FLT-PET than FDG-PET (Odds ratio = 3.67; P=0.004). The optimal SUVmax cutpoint for FLT-PET to correspond with positive FDG-PET for the matched lymph nodes was 3.25 (range 3.1–3.4). Conclusions. It is unlikely that FLT-PET will be a more accurate staging investigation than FDG-PET. A SUVmax of 3.25 may be considered as a reference cut-off in determining if a cervical lymph node is involved for HNSCC. Validation in a surgical cohort with pathological correlation is warranted.