CAN POSITRON-EMISSION-TOMOGRAPHY DISTINGUISH TUMOR RECURRENCE FROM IRRADIATION SEQUELAE IN PATIENTS TREATED FOR LARYNX CANCER

PURPOSE Distinguishing persistent or recurrent tumor from postradiatio n edema or soft-tissue/cartilage necrosis in patients treated for carc inoma of the larynx can be difficult. Because recurrent tumor is often submucosal, multiple deep biopsies may be necessary before a diagnosi s can be established. Positron emission tomography with F-18 fluorodeo xyglucose was studied for its ability to aid in this problem. PATIENTS AND METHODS FDG PET scans were performed on 31 patients who were susp ected of having persistent or recurrent tumor after radiation treatmen t for carcinoma of the larynx. Patients underwent thorough history and physical examinations, scans with computed tomography (23 patients), and pathological evaluation when indicated. PET scans were interpreted by each of the two radiologists, who were blinded to patient outcome and the other's report. RESULTS The time between completion of radiati on treatment and positron emission tomography examination ranged from 2 to 61 months with a median of 6 months. Fifteen patients had patholo gical evidence of tumor in the larynx, while 16 have remained without evidence of disease. The overall sensitivity and specificity of the po sitron emission tomography interpretations were 80% and 81%, respectiv ely. The sensitivity and specificity of the computed tomography scan i nterpretations were 58% and 100%, respectively. Of the 23 patients wit h computed tomography scans, eight patients acquired useful informatio n from the positron emission tomography, three patients had incorrect positron emission tomography interpretations and correct computed tomo graphy interpretations, and one patient had positive tumor despite a n egative positron emission tomography and computed tomography. DISCUSSI ON Positron emission tomography is useful in distinguishing benign fro m malignant changes in the larynx after radiation treatment. This noni nvasive technique can supplement information provided by computed tomo graphy scans. It is reasonable to delay biopsy, which could traumatize radiation-damaged tissues and precipitate necrosis, for those patient s with negative positron emission tomography scans who have clinical s igns and symptoms associated with recurrence.