Relationships between preoperative FMISO- and FDG-PET parameters and the prognosis in patients with oral squamous cell carcinoma

Objectives Hypoxic tumors are considered to be resistant to chemotherapy and radiotherapy. Moreover, some PET parameters and clinical factors are reported as prognostic factors in patients with oral squamous cell carcinoma (OSCC). The aim of this study was to elucidate the relationships between preoperative FMISO- and FDG-PET or clinical parameters and the prognosis after surgery in patients with OSCC.

Methods A total of 40 patients (Age: 29-92; M/F: 25/15) with OSCC who underwent radical surgery were enrolled in this study. The primary tumor sites were the lower gingiva (n=14), tongue (n=12), upper gingiva (n=8), buccal mucosa (n=4), and oral floor (n=2). Three tumors were classified as T1, 17 as T2, five as T3, and 15 (48%) as T4a. The N-classifications were N0 in 28 patients, N1 in seven, and N2 in five. Each patient underwent FMISO- and FDG-PET CT before surgery. Neck dissection was performed in 23 patients. None and 10 patients received pre- and postoperative radiotherapy, respectively. The averaged postoperative period was 40±17 months. The hypoxic volume (HV) of the tumor was measured by FMISO-PET CT, defining as hypoxic area if FMISO tumor to muscle ratio (TMR) was more than 1.25. Metabolic tumor volume (MTV) was measured using the cut off values with 2.5 of SUV max of FDG-PET. Locoregional recurrence, Overall survival (OS) and disease free survival (DFS) rates are evaluated using Kaplan-Meier method and Log-rank test.

Results During follow-up after radical surgery, there were 13 locoregional recurrences, 2 distant metastases, and 7 deaths. The median (range) of HV of cancer and FMISO-PET TMR were 0.5 (0-35 ml) and 1.4 respectively. The median (range) of FDG-PET SUV max, and MTV were 15.5 (1.0-32.2), and 9.6 (0.3-92.3 ml), respectively. There were no significant relations between the locoregional recurrence or disease-specific death and gender of the patients (Ps=0.43 and 0.75), pT-stage (Ps=0.74 and 0.68), pN-stage (Ps=0.42 and 0.42), HV (Ps=0.74 and 0.68), FMISO TMR (Ps=0.39 and 0.68), FDG SUV max (Ps=0.74 and 0.68), and MTV (Ps=0.91 and 0.58). Log-rank tests revealed no significant relations between OS or DFS and HV (Ps=0.74 and 0.78), FMISO TMR (Ps=0.14 and 0.77), FDG SUV max (Ps=0.73 and 0.77), and MTV (Ps=0.56 and 0.97) in our surgically treated OSCC patients.

Conclusions This study may indicate limited values of preoperative PET parameters for predicting the prognosis of the surgically treated patients with OSCC.

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