Monitoring of response to radiotherapy with fluorine-18 deoxyglucose PET of head and neck squamous cell carcinomas

We examined the usefulness of positron emission tomography (PET) using fluo rine-18 deoxyglucose (FDG) in determining the therapeutic effects of irradi ation and chemotherapy on head and neck malignant tumors. Twenty-two patien ts with head and neck lesions who underwent histological examinations were studied. Squamous cell carcinoma was histologically diagnosed in all cases. Sixteen of them underwent radiotherapy with approximately 40 Gy in combina tion with carboplatin therapy. The remaining 6 patients underwent radiother apy alone. After these treatments, ii underwent surgery. For PET study, eac h patient was injected with intravenous FDG 185-370 MBq. We evaluated the d egree of FDG accumulation using scanned images taken 40-55 min after the in jection. We measured the standardized uptake value (SUV), a semiquantative evaluation, ROI activity divided by the dosage per weight of each patient. FDG-PET, CT and MRI were performed twice for each patient, before and after treatment. FDG uptake, but not the tumor size in CT or MRI, was significan tly reduced in each patient after the treatment. Therefore, our findings ha ve clearly demonstrated that FDG-PET provides for more valuable therapeutic outcomes than conventional imaging such as CT and MRI. FDG-PET should thus provide a new dimension in the management of head and neck malignant tumor s.