Pattern and predictors of false positive lymph node involvement on positron emission tomography in patients with...

Objectives The aim of this study was to elucidate the optimal parameters for diagnosing false positive (FP) lymph nodes (LNs) in patients with non-small cell lung cancer.Methods We reviewed 292 patients with non-small cell lung cancer (NSCLC). Fluorodeoxyglucose positron emission tomography (FDG-PET) imaging was performed at 1 hour (early) post-FDG injection and repeated 2 hours (delayed) after injection. We analyzed the relationship between the pathology of LNs and the results of PET, and the percent change in the standardized uptake value (%ΔSUV) between the two time-points.Results Eighteen of 46 cases (39.1%) in the FP group showed higher SUVs for their LNs compared with those for primary tumor, whereas 13.2% in the true positive group (p = 0.032) had higher SUVs for their LNs. Thirty-four of 36 cases in the true positive group had %ΔSUV ranging from 0% to 61.5% compared with only 13 of 33 in the FP group. Twenty out of 22 cases (90.9%) where %ΔSUV was over 61.5% or under 0% were considered as FP.Conclusions Patients with higher SUVs for LNs than for primary tumors and patients with extremely high or low %ΔSUVs tended to have FP LNs.