Positron emission tomography–computed tomography before treatment is highly prognostic of distant metastasis in nasopharyngeal carcinoma patients after intensity-modulated radiotherapy treatment: A prospective study with long-term follow-up

SummaryObjectivesThe utility of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the prediction of distant metastasis after definitive treatment for non-disseminated NPC patients is not clear. We prospectively investigated the prognostic significance of 18F-FDG PET-CT performed before treatment for the distant metastasis-free survival (DMFS) of NPC patients treated with intensity-modulated radiotherapy (IMRT) ± chemotherapy.Materials and methodsThe results of PET-CT scans performed at initial diagnosis were recorded and analyzed prospectively. Patients then received standard treatment per protocol independent of the PET-CT result. IMRT was administered to the nasopharynx and neck. Early stage patients received IMRT alone, whereas loco-regionally advanced patients received concurrent chemoradiation. Patient outcomes were evaluated.ResultsOne hundred and seventy-nine patients were analyzable. DM occurred in 33 patients and the 3-year DMFS rate of the whole cohort was 84.1%. The cut-off of the SUVmax at the primary site (SUVmax-P) for DMFS was 10.22 by ROC curve. The 3-year DMFS rates of the higher and lower SUVmax-P groups (SUVmax-P ⩽ or > 10.22) were 93.2% and 75.1%, respectively, with an 18.1% difference (P = 0.003). Multivariate analysis indicated that SUVmax-P was a risk factor independently associated with DMFS (HR, 2.672; 95%CI, 1.236–5.776; P = 0.012) and OS (HR, 2.417; 95%CI, 1.313–4.448; P = 0.005). Subgroup analysis indicated that the 5-year DMFS and OS in loco-regionally advanced patients with SUVmax-P ⩽ 10.22 were similar to those of early stage patients, whereas those of loco-regionally advanced patients with SUVmax-P > 10.22 patients predicted worse outcome.ConclusionSUVmax-P is a useful biomarker to predict distant metastasis of NPC patients treated with IMRT. Combining SUVmax-P with tumor overall stage, a more precise picture could be obtained to predict treatment outcome.