DISTINGUISHING TUMOR RECURRENCE FROM IRRADIATION SEQUELAE WITH POSITRON EMISSION TOMOGRAPHY IN PATIENTS TREATED FOR LARYNX CANCER

Purpose: Distinguishing persistent or recurrent tumor from postradiati on edema, or soft tissue/cartilage necrosis in patients treated for ca rcinoma of the larynx can be difficult. Because recurrent tumor is oft en submucosal, multiple deep biopsies may be necessary before a diagno sis can be established. Positron emission tomography with 18F-2fluoro- 2deoxyglucose (FDG) was studied for its ability to aid in this problem . Methods and Materials: Positron emission tomography (18FDG) scans we re performed on II patients who were suspected of having persistent or recurrent tumor after radiation treatment for carcinoma of the larynx . Patients underwent thorough history and physical examinations, scans with computerized tomography, and pathologic evaluation when indicate d. Standard uptake values were used to quantitate the FDG uptake in th e larynx. Results: The time between completion of radiation treatment and positron emission tomography examination ranged from 2 to 26 month s with a median of 6 months. Ten patients underwent computed tomograph y (CT) of the larynx, which revealed edema of the larynx (six patients ), glottic mass (four patients), and cervical nodes (one patient). Pos itron emission tomography scans revealed increased FDG uptake in the l arynx in five patients and laryngectomy confirmed the presence of carc inoma in these patients. Five patients had positron emission tomograph y results consistent with normal tissue changes in the larynx, and one patient had increased FDG uptake in neck nodes. This patient underwen t laryngectomy, and no cancer was found in the primary site, but nodes were pathologically positive. One patient had slightly elevated FDG u ptake and negative biopsy results. The remaining patients have been fo llowed for 11 to 14 months since their positron emission studies and t heir examinations have remained stable. In patients without tumor, ave rage standard uptake values of the larynx ranged from 2.4 to 4.7, and in patients with tumor, the range was 4.9 to 10.7. Conclusion: Positro n emission tomography with labeled FDG appears to be useful in disting uishing benign from malignant changes in the larynx after radiation tr eatment. This noninvasive technique may be preferable to biopsy, which could traumatize radiation-damaged tissues and precipitate necrosis.