Appropriate timing of surveillance intervals with whole-body ¹⁸F-FDG PET/CT following treatment for sinonasal malignancies

PURPOSE: To assess the ideal timing of posttreatment whole-body 18F-FDG PET/CT examination as routine surveillance to determine local recurrence (R), lymph node metastasis (LM), and distant metastasis (DM) of sinonasal malignancies and to investigate the effect of 18F-FDG PET/CT on survival.

METHODS: An overall 80 patients who had undergone a total of 197 posttreatment whole-body 18F-FDG PET/CT examinations for sinonasal malignancy were retrospectively examined after institutional review board approval. Patients were grouped regarding the time intervals (<1 month, 1-3 months, 3-6 months, 6-12 months, 12-18 months and >18 months) after the conclusion of treatment. Differences in diagnostic accuracy due to different follow-up intervals were calculated by receiver operator curves (ROC) and a Cox proportional hazards model was used to assess the prognostic value of surveillance 18F-FDG PET/CT.

RESULTS: Considering the time intervals of posttreatment 18F-FDG PET/CT scans, the negative predictive value and positive predictive value of the 18F-FDG PET/CT examinations to predict overall recurrence in 1-3 months (100 and 100%, respectively) and >18 months (100 and 95%, respectively) were higher than for recurrence detection in <1 month (50 and 100%, respectively), 3-6 months (81 and 93%, respectively), 6-12 months (79 and 87%, respectively), and 12-18 months (75 and 80%, respectively) (p < 0.05). Positive findings on 18F-FDG PET/CT scans were also independent predictors of poorer overall survival (OS) (p < 0.05).

CONCLUSIONS: Whole-body 18F-FDG PET/CT is capable of identifying recurrences following treatment, using an optimal time interval for scanning of 1-3 months and >18 months after therapy.