[18F]fluoro-2-deoxyglucose-positron emission tomography for the assessment of histopathological response after preoperative chemoradiotherapy in advanced oral squamous cell carcinoma

[F-18]fluoro-2-deoxyglucose-positron emission tomography (FDG-PET) is widely used to evaluate tumor metabolic activity. The aim of this study was to evaluate the usefulness of FDG-PET in assessing the histopathological response to preoperative concurrent chemoradiotherapy (CRT) in patients with oral squamous cell carcinoma (OSCC). Forty-five patients with resectable advanced OSCC who had received preoperative CRT followed by tumor ablative surgery between January 2004 and December 2011 were included in the study. All patients underwent FDG-PET before and after preoperative CRT. The maximum standardized uptake value (SUVmax) before (pre-SUV) and after preoperative CRT (post-SUV) and the SUVmax reduction rate (Delta SUV %) were used to evaluate the response to preoperative CRT. Correlations among SUVmax, histopathological response, and expression of cancer antigen Ki-67 and hypoxia-inducible factor-1 alpha (HIF-1 alpha) were analyzed. Preoperative CRT significantly reduced intratumoral FDG uptake (P < 0.001). The pre-SUV and post-SUV were significantly lower in patients with a pathological complete response (pCR) than in those with a non-pCR (pre-SUV P = 0.037; post-SUV P = 0.001). Delta SUV % was higher in patients with pCR than in those with non-pCR (P = 0.029). The pre-SUV was significantly correlated with Ki-67 and HIF-1 alpha expression in pretreatment biopsy specimens (Ki-67 P = 0.046, R = 0.292; HIF-1 alpha P = 0.007, R = 0.385). The expression of both Ki-67 and HIF-1 alpha was significantly lower in patients with pCR than in those with non-pCR (Ki-67 P < 0.001; HIF-1 alpha P < 0.001). Low pre-SUV and post-SUV and high Delta SUV % may predict a good histopathological response to preoperative CRT. Ki-67 and HIF-1 alpha expression in pretreatment biopsy specimens were predictors of histopathological response to preoperative CRT.