Accurate FDG PET tumor segmentation using the peritumoral halo layer method: a study in patients with esophageal squamous cell carcinoma

BACKGROUND: In a previous study, FDG PET tumor segmentation (SegPHL) using the peritumoral halo layer (PHL) was more reliable than fixed threshold methods in patients with thyroid cancer. We performed this study to validate the reliability and accuracy of the PHL method in patients with esophageal squamous cell carcinomas (ESCCs), which can be larger and more heterogeneous than thyroid cancers. METHODS: A total of 121 ESCC patients (FDG avid = 85 (70.2%); FDG non-avid = 36 (29.8%)) were enrolled in this study. In FDG avid ESCCs, metabolic tumor length (ML) using SegPHL (ML(PHL)), fixed SUV 2.5 threshold (ML(2.5)), and fixed 40% of maximum SUV (SUVmax) (ML(40%)) were measured. Regression and Bland-Altman analyses were performed to evaluate associations between ML, endoscopic tumor length (EL), and pathologic tumor length (PL). A comparison test was performed to evaluate the absolute difference between ML and PL. Correlation with tumor threshold determined by the PHL method (PHL tumor threshold) and SUVmax was evaluated. RESULTS: ML(PHL), ML(2.5), and ML(40%) correlated well with EL (R(2) = 0.6464, 0.5789, 0.3321, respectively; p < 0.001) and PL (R(2) = 0.8778, 0.8365, 0.6266, respectively; p < 0.001). However, ML(2.5) and ML(40%) showed significant proportional error with regard to PL; there was no significant error between ML(PHL) and PL. ML(PHL) showed the smallest standard deviation on Bland-Altman analyses. The absolute differences between ML and PL were significantly smaller for ML(PHL) and ML(40%) than for ML(2.5) (p < 0.0001). The PHL tumor threshold showed an inverse correlation with SUVmax (σ = − 0.923, p < 0.0001). CONCLUSIONS: SegPHL was more accurate than fixed threshold methods in ESCC. The PHL tumor threshold was adjusted according to SUVmax of ESCC.