Automated Cosegmentation of Tumor Volume and Metabolic Activity Using PET-CT in Non-Small Cell Lung Cancer (NSCLC)

Abstract

Purpose/Objective(s): This study presents a novel computer-aided, automatic contouring (co-segmentation) gross target volume (GTV) that integrates tumor boundaries on both PET and CT through a globally optimal graph-based algorithm. Metabolic TV (MTV) was developed by integration of co-segmented tumor boundaries and metabolic activities as a tumor response metric. Materials/Methods: Records of 649 lung cancer patients were reviewed. Patients with stage III/IV NSCLC who received chemotherapy and lung radiation and had PET-CT imaging for simulation and PET-CT/CT at 2-4 months follow-up post-radiation were included. A total of 19 patients fulfilled the criteria. Post-treatment residual GTV (post-GTV) was retrospectively contoured by physician. A co-segmented GTV was generated on pretreatment PET-CT. MTV was defined as co-segmented GTV times mean SUV. As tumor response metrics, co-segmented GTV, co-segmented MTV, and mean SUV were generated on pretreatment dataset and tested for correlation with a pre-treatment, physician contoured GTV (pre-GTV) that was used as a ground truth for comparison. Their correlations with physician’s contour were measured using spearman’s correlation coefficient. Linear regression was used to evaluate if the different metric was predictive of post-GTV. Tumor response after chemoradiation therapy was measured using preand post-GTV. Results: Co-segmented GTV and MTV significantly correlated with pre-GTV (p < 0.001). Co-segmented GTV (p < 0.0001), co-segmented MTV (p Z 0.0009), pre-GTV (p < 0.0001) significantly correlated with post-GTV. No significant correlation was found in mean SUV (p Z 0.74). The overall averaged tumor response rate after chemoradiation therapy in 2-4 months is 69.5% +/-19.2%. Squamous cell histology responded better by 20% compared to adenocarcinoma. Tumor response pattern was modeled as post-GTV Z 10.0 + 0.4*pre-GTV (R Z 0.68). Conclusions: Co-segmented GTV and MTV present significant correlations with physician’s manual contouring, showing potential as a tumor response evaluation tool for large scale clinical trials and daily clinical practice. Average local tumor response in 2-4 months for advanced stage NSCLC after chemoradiation therapy was 69.5%. Author Disclosure: H. Li: None. J. Bai: None. T. Abu Hejle: None. X. Wu: None. S. Bhatia: None. Y. Kim: None.