Clinical usefulness of PET in the management of oral cancer. Comparison between FDG-PET and MET-PET

Inductive chemoradiotherapy has played an important role in preserving organs and functions in patients with oral squamous cell carcinoma (SCC). To determine whether a reduced form of surgery should be performed after chemoradiotherapy, accurate evaluation of residual tumor cells is essential. We investigated the clinical value of positron emission tomography with 18F labeled fluorodeoxyglucose (FDG-PET) in the management of oral SCCs. Forty-five patients underwent two FDG-PET studies, one prior to and one at 6 weeks after the chemoradiotherapy. Pretreatment FDG-PET was useful in predicting the response to treatment. Posttreatment FDG-PET could evaluate residual viable cells and prognosis. Organ preservation may be feasible based on PET evaluation. Hence FDG-PET is a valuable tool in the treatment of oral cancer. 11C-Methionine (MET) is another promising tracer for PET that can be used to assess metabolic demand for amino acids in cancer cells. A MET-PET and FDG-PET study was performed during the same period to investigate diagnostic accuracy in 40 oral malignancies. Sensitivity and positive predictive value of MET-PET were 95% and 100%, respectively, and were comparable with those of FDG-PET. Further study is required to determine the diagnostic significance of MET-PET in evaluating response to chemoradiotherapy. (author)