POSITRON EMISSION TOMOGRAPHY OF PATIENTS WITH HEAD AND NECK-CARCINOMABEFORE AND AFTER HIGH-DOSE IRRADIATION

Background. Positron emission tomography (PET) with labeled fluorodeox yglucose (FDG) demonstrates increased tracer uptake in many neoplasms. This study was undertaken to define the patterns of FDG uptake in hea d and neck neoplasms before and after high dose irradiation. Methods. Twenty-five patients were evaluated prospectively with PET and standar d clinical and radiographic techniques before and after irradiation. R esults. Twenty-seven primary sites were confirmed pathologically in 23 patients and included the nasopharynx (four lesions), oropharynx (14 lesions), larynx (five lesions), oral cavity (two lesions), and parana sal sinuses (two lesions). Two patients had unknown primary sites. Twe nty-four of 27 primary sites correlated with areas of increased tracer uptake on PET scans. Five patients had increased uptake in cervical l ymph nodes that were uninvolved by radiographic or clinical criteria. Positron emission tomography seemed to be able,to differentiate tumor activity from fluid-filled sinuses in two patients with paranasal sinu s tumors. In two patients with unknown primary sites, increased uptake in the base of tongue after PET suggested occult primary sites. Posit ron emission tomography scans obtained 1 month after high dose irradia tion (RT) indicated decreased levels of FDG uptake in all patients' tu mors. However, these scans did not accurately reflect the status of di sease in these patients. Scans obtained 4 months after RT were believe d to assess more accurately the presence of malignancy. Conclusions. P ositron emission tomography is a new modality that may be useful in de fining tumor activity in clinically negative areas. Appropriately time d posttreatment PET may be useful in predicting outcome after definiti ve RT and in distinguishing viable tumors from normal tissue changes a fter RT in patients with head and neck carcinomas.