The Utility of PET/CT in Staging and Assessment of Treatment Response of Nasopharyngeal Cancer

Introduction: The aim of this study was to evaluate the impact of positron emission tomography/computerised tomography (PET/CT) as an adjunct to conventional imaging (CI) in the management of nasopharyngeal cancer (NPC) both for initial staging and assessment of post-treatment response.

Methods: All NPC cases referred to the Peter MacCallum Centre for Metabolic Imaging between January 2002 and December 2007 were identified. In patients undergoing initial staging, any differences between the pre-PET/CT management plan based on CI and that following performance of the PET/CT scan were noted. Clinical impact was scored using the Centre's published criteria: 'high' if PET/CT changed the primary treatment modality or intent, 'medium' if treatment modality was unchanged but the radiotherapy technique or dose was altered, and 'low' if there was no change in treatment modality or intent. Patients undergoing PET/CT following definitive treatment were scored according to whether or not they achieved a complete metabolic response.

Results: Forty-eight patients underwent a staging PET/CT. The clinical impact was high in 8%, medium in 25% and low in 66% of patients. Twenty-one patients were scanned for post-treatment response. PET/CT was less frequently equivocal than MRI (3 vs 8/21). A complete metabolic response on PET/CT was associated with a 93% negative predictive value for subsequent recurrence.

Conclusion: PET/CT is a valuable staging tool for the detection of occult metastatic disease and defining the extent of neck nodal disease. Post-treatment, a complete metabolic response on PET/CT has a very high negative predictive value with fewer equivocal results than MRI.