Predictive value of volumetric parameters measured by F-18 FDG PET/CT for lymph node status in patients with surgically resected rectal cancer

The objective of this study was to investigate the predictive role of volumetric parameters such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG) measured by F-18 FDG PET/CT for regional lymph node (rLN) metastasis in rectal cancer patients. Retrospectively, 74 rectal cancer patients were enrolled. All patients received surgical treatment and F-18 FDG PET/CT at diagnosis. The F-18 FDG PET/CT findings of primary cancer and rLN involvement were compared with the pathologic diagnosis within 5 weeks after operation. Univariate and multivariate analyses were used to analyze the associations among the pathologic LN status and age, sex, T stage, AJCC stage, SUVmax, lymphatic invasion, venous invasion, neural invasion, and volumetric parameters. The LN (+) group showed statistically significant higher values of MTV2.5 (p < 0.0001) MTV3 (p < 0.0001), MTV3.5 (p=0.0001), TLG2.5 (p=0.0007), TLG3 (p=0.0011), and TLG3.5 (p=0.0024). In univariate analysis, T stage, AJCC stage, neural invasion, and volumetric parameters were factors significantly associated with pathologic LN involvement. However, in multivariate analysis, advanced T stage, high AJCC stage, MTV2.5, and TLG2.5 were associated with pathologic LN involvement in rectal cancer. This study showed that, not only T stage and AJCC stage, but also volumetric parameters such as MTV2.5 and TLG2.5 are useful factors for the prediction of pathologic LN status in rectal cancer patients. (author)