Semi-Automated Co-Segmentation of Tumor Volume Using Multimodality Pet-Ct in Non-Small Cell Lung Cancer (NSCLC)

Introduction: Lung cancer is the most commonly occurring cancer for both men and women with the highest associated mortality rate. Positron emission tomography and computed tomography (PET-CT) are accurate evaluation modalities in determining lung cancer extent and aggression. An efficient and reliable computerized tumor volume (TV) delineation system, based on PET-CT maging is needed for accurate tumor response analysis during daily clinical practice and in large clinical trial. Purpose: To present and validate a novel computer-aided, semi-automatic co-segmentation method for lung tumor volume (co-segmented TVPET-CT) that integrates tumor boundaries on both PET and CT. Methods and Materials: Eighteen patients were included all of whom had stage III/IV NSCLC had received chemoradiotherapy, PET-CT simulation preradiotherapy and a CT scan at 2-4 months follow-up post-radiotherapy. Preradiotherapy GTV (pre-GTV) on PET-CT images were retrospectively contoured by two physicians who reached consensus on the volume and then used this as the reference tumor volume. The statistical correlation were analyzed between the reference tumor volume and different segmented tumor volumes; cosegmented TVPET-CT, segmented Tumor Volume on CT alone (TVCT), segmented Tumor Volume on PET alone (TVPET), Tumor Volume (TVSUV2.5) delineated using the SUV2.5 threshold, and Tumor Volume (TVSUVmean) using the SUVMEAN threshold. Results: The co-segmented TVPET-CT showed the most significant correlation with pre-GTV (correlation coefficient = 0.993), along with the most favorable ASSD (1.48 ± 0.8 mm) and DSC values (0.85 ± 0.07). TVSUV2.5, TVCT, TVPET, and post-GTV significantly correlated with pre-GTV (P < 0.001) except for TVSUVmean (P = 0.42). Smoking status and histology presented significant correlationwith %ΔTV (P = 0.0273 and P = 0.0297 respectively) while no significant correlations in gender, age, and stage were evident. None of other computeraided segmented tumor volumes or SUVs correlated with %ΔTV. The overall averaged tumor response rate after chemoradiotherapy in 2 - 4 months is 70 ± 18.6%. Conclusion: The co-segmented tumor volume on PET-CT was most strongly correlated with two-physician-consensus manual contouring that clinically incorporates PET and CT information.