The value of F-18 FDG PET/CT in nasopharyngeal carcinoma: Cervical LN staging and prognosis

Objectives To assess the value of F-18 FDG PET/CT in planning treatment and the prognostic significance of metabolic parameters of primary tumor in nasopharyngeal carcinoma (NPC).

Methods Initial PET/CT for NPC taken from December 2003 to April 2011 were retrospectively studied. CT and/or MRI had been performed within 1 month of PET/CT. On cervical lymph node (LN) staging, final diagnosis was based on follow-up of 6 months or longer. Metabolic parameters were measured as maximum standardized uptake value (SUVmax) and metabolic tumor volume (MTV) of primary tumor. SUVmax, MTV, SUVmax for primary tumor to mean SUV for liver ratio (T/L ratio), age, stage and histology were analyzed for association with progression-free survival (PFS) and overall survival (OS).

Results Forty-nine patients (mean age 55 ± 12.1, male 30, female 19) were included. Initial PET/CT showed distant metastases in 10 patients, and treatment plans were changed from concurrent chemoradiation therapy to systemic chemotherapy in 9 patients (18.4%). The cervical LN detection sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were 93.6%, 92.1%, 93.1%, 95.8% and 88.1%, retrospectively, for PET/CT, and 91.3%, 71.9%, 84.7%, 86.3% and 81.0% for conventional imaging studies (CIS). The specificity, accuracy, PPV and NPV of PET/CT were significantly higher than those of CIS (p<0.001, p=0.0035, p<0.001, p=0.0334). Mean follow up was 24.7 ± 20.8 months. On multivariate analysis, high T/L ratio is significantly associated with PFS (p=0.007, HR 20.705, 95% CI 2.323-184.529). T stage is not associated with PFS, however, T3 stage shows significantly poor prognosis compared with T1 stage (p=0.045, HR 8.307, 95% CI 1.048-65.867).

Conclusions Treatment plans were changed on account of initial PET/CT in 18.4% of patients with nasopharyngeal carcinoma. PET/CT demonstrated higher specificity, accuracy, PPV and NPV for detecting cervical LN metastasis than CIS. High FDG uptake and extent of tumor may predict tumor recurrence