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

BACKGROUND: [(18)F]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). METHODS: 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 (ΔSUV %) 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-1α (HIF-1α) were analyzed. RESULTS: 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). ΔSUV % 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-1α expression in pretreatment biopsy specimens (Ki-67 P = 0.046, R = 0.292; HIF-1α P = 0.007, R = 0.385). The expression of both Ki-67 and HIF-1α was significantly lower in patients with pCR than in those with non-pCR (Ki-67 P < 0.001; HIF-1α P < 0.001). CONCLUSIONS: Low pre-SUV and post-SUV and high ΔSUV % may predict a good histopathological response to preoperative CRT. Ki-67 and HIF-1α expression in pretreatment biopsy specimens were predictors of histopathological response to preoperative CRT.

Efficacy of FDG-PET for defining gross tumor volume of head and neck cancer.

We analyzed the data for 53 patients with histologically proven primary squamous cell carcinoma of the head and neck treated with radiotherapy between February 2006 and August 2009. All patients underwent contrast-enhanced (CE)-CT and (18)F-fluorodeoxyglucose (FDG)-PET before radiation therapy planning (RTP) to define the gross tumor volume (GTV). The PET-based GTV (PET-GTV) for RTP was defined using both CE-CT images and FDG-PET images. The CE-CT tumor volume corresponding to a FDG-PET image was regarded as the PET-GTV. The CE-CT-based GTV (CT-GTV) for RTP was defined using CE-CT images alone. Additionally, CT-GTV delineation and PET-GTV delineation were performed by four radiation oncologists independently in 19 cases. All four oncologists did both methods. Of these, PET-GTV delineation was successfully performed in all 19 cases, but CT-GTV delineation was not performed in 4 cases. In the other 15 cases, the mean CT-GTV was larger than the PET-GTV in 10 cases, and the standard deviation of the CT-GTV was larger than that of the PET-GTV in 10 cases. Sensitivity of PET-GTV for identifying the primary tumor was 96%, but that of CT-GTV was 81% (P < 0.01). In patients with oropharyngeal cancer and tongue cancer, the sensitivity of CT-GTV was 63% and 71%, respectively. When both the primary lesions and the lymph nodes were evaluated for RTP, PET-GTV differed from CT-GTV in 19 cases (36%). These results suggested that FDG-PET is effective for defining GTV in RTP for squamous cell carcinoma of the head and neck, and PET-GTV evaluated by both CE-CT and FDG-PET images is preferable to CT-GTV by CE-CT alone.

Axillary lymph node accumulation on FDG-PET/CT after influenza vaccination.

OBJECTIVE: 2-[(18)F]fluoro-2-deoxy-D: -glucose (FDG) is known to accumulate in benign conditions such as infection and inflammation as well as in malignancy. Vaccination may cause transient inflammation of lymph nodes, which may induce false-positive findings on FDG-positron emission tomography (PET) imaging. This study investigated the influence of influenza vaccination on FDG-PET/CT imaging in normal subjects. METHODS: Between November 2008 and March 2009, a total of 172 examinees underwent FDG-PET/CT during an annual cancer-screening program at our hospital, 83 of whom had a history of recent non-adjuvanted seasonal influenza vaccination. They were asked the date and injection site of the vaccination. Examinees were divided into 2 groups based on the interval after vaccination using a cutoff value of 7 days (1 week). Two double board-certified nuclear medicine physicians and radiologists visually interpreted the FDG-PET/CT images with reference to PET/CT fusion and CT images and checked the location and the number of abnormal accumulations by consensus reading. RESULTS: Intervals between vaccination and FDG-PET were less than 7 days in 5 examinees, and 7 days or more in 78 examinees. Unexpected accumulations were visualized in 4 examinees in the axilla and medial upper arm, and all of them belonged to the group who underwent vaccination less than 7 days previously. In the second group there was no abnormal FDG accumulation. CONCLUSIONS: Recent influenza vaccination before FDG-PET/CT examination may cause ipsilateral axillary lymph node accumulations, especially within several days after vaccination. Questionnaires about vaccination can help to avoid false interpretation of FDG avid axillary lymph nodes.