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.