The added value of ¹⁸F-FDG-PET-CT compared with conventional Imaging modalities in paediatric nasopharyngeal carcinoma

Objectives: To explore the impact of ¹⁸F-FDG-PET/CT in paediatric nasopharyngeal carcinoma (PNPC) either during initial staging or re-staging after end of therapy versus conventional imaging modalities (MRI and CT).

Methods: Forty patients with biopsy proven PNPC (mean age 13±2.3; range 9-17 years, 29 males and 11 females) mostly of non-keratinizing undifferentiated type III (95%) were included in the study. Whole body ¹⁸F-FDG-PET/CT, MRI and Ce-CT of the head and neck were obtained in all patients, as well as MRI and Ce-CT of the chest, abdomen and pelvis (the interval between the different modalities ranged from 2-28 days). The findings of PET/CT were compared with those of conventional imaging (CI) modalities regarding TNM staging either initially or after end of therapy. Tissue biopsy and/or clinical follow-up were used as control criteria for the nature of the detected lesions.

Results: The studied group of patients was divided into two categories for analysis; 21 patients were analyzed at initial staging (52.5%) and 19 patients (47.5%) were analyzed for restaging after end of 1st line of therapy. In initial staging; The T stage detectability revealed a higher sensitivity for MRI versus PET/CT and Ce-CT with sensitivities’ of 95.2%, 100% and 94.1% for PET/CT, MRI and CT, respectively. Regarding the N stage; PET/CT showed higher sensitivity than CI modalities with sensitivity values of 95.2%, %, and 88.8% and 77.7% for PET/CT, MRI, and CT, respectively. In respect to the M stage; the sensitivity values were 80%, 60% and 25% for PET/CT, MRI, and CT, respectively. PET/CT upstaged 3 cases and 6 cases compared with MRI and CT, respectively. In re-staging; PET/CT had better diagnostic results than CI modalities as regards sensitivity, specificity, positive predictive value and negative predictive value for local residual/recurrence (T) being (100%, 75%, 93.8% and 100% versus 86%, 75%, 92.8% and 60%, respectively) as well as for nodal detection (N) being (100%, 85.7%, 92.3% and 100% versus 100%, 57%, 80% and 100%, respectively). For distant metastases (M), PET/CT showed a higher sensitivity of 100% compared with only 66% for both CI modalities. On follow up, ¹⁸F-FDG-PET/ changed disease stage in 4/19 patients (21%) by upstaging two cases and down staging two cases

Conclusion: ¹⁸F-FDG-PET/CT is considered a potentially valuable imaging tool in PNPC either in initial staging or restaging which could effectively change the overall staging and hence the management. Research Support: none