Defining risk groups of patients with cancer of unknown primary site and cervical nodal metastases by F‐18 fluorodeoxyglucose positron emission tomography and computed tomography imaging

Abstract

We sought to investigate the clinical utility of F-18 fluorodeoxyglucose (FDG) positron emission tomography and computed tomography (PET/CT) in Taiwanese patients with cancer of unknown primary site (CUP) and cervical nodal metastases. We also aimed to study the impact of F-18 FDG PET/CT on clinical treatment priority in this patient group. Between September 2006 and May 2014, patients with CUP and cervical nodal metastases who underwent F-18 FDG PET/CT imaging study were retrospectively identified. The clinicopathological risk factors and PET parameters were analyzed in relation to 2-year overall survival (OS) rates using univariate and multivariate analyses. Two-year OS curves were plotted with the Kaplan-Meier method. Of the eligible patients (n = 54), 12 (22.2%) had distant metastases (DM) at presentation. A total of 13 (24.1%) and 15 (27.8%) primary tumors were identified by FDG PET/CT imaging and an additional triple biopsy, respectively. The results of multivariate analysis identified smoking [p = 0.033, 95% confidence interval (CI) = 1.197-40.342], a maximum standardized uptake value (SUVmax) of cervical nodes ≥ 14.2 (p = 0.035, 95% CI = 1.134-28.029), and DM at presentation (p = 0.031, 95% CI = 1.257-114.854) as independent predictors of 2-year OS. Specifically, patients who carried ≥ 2 risk factors showed poorer outcomes (70.3% vs. 11.8%, p < 0.001). Fifteen study patients (27.8%) had their treatment modified by FDG PET/CT findings. We conclude that FDG PET/CT is clinically useful in CUP patients not only for tumor staging, but also for modifying treatment regimens.

The Diagnostic Contribution of (18)F-FDG PET/CT Scan in Cancer of Unknown Primary

“…18 F-FDG PET/CT scan is important in the detection of the primary site in patients with CUP with a success rate of 27%, after all other conventional imaging modalities have failed 15 . The diagnostic accuracy of 18 F-FDG PET/CT imaging in patient with CUP group is influenced by a number of factors, including the tumor biological behavior, size, and anatomical location 16 . In respect of determining primary localization, 18 F-FDG PET/CT's sensitivity was determined as 66.6%, its specificity as 33.3%, its positive predictive value as 80%, and its negative predictive value as 20% 17 .…”