Diagnostic value of computed tomography (CT) and positron emission tomography (PET) for paraaortic lymph node metastasis from left-sided colon and rectal cancer

Abstract

Paraaortic lymph node (PALN) metastasis influences treatment strategy for colorectal cancer. The aims of this study were to elucidate the diagnostic value of computed tomography (CT) and positron emission tomography (PET) for PALN metastasis from left-sided colorectal cancer. A total of 108 patients who underwent radical surgery including PALN dissection were included. Size and morphology of PALN were evaluated using CT, and presence of higher FDG uptake was evaluated using PET. Findings of CT and PET were compared with pathological status. The largest major axis ≥11mm and heterogeneous internal density were predictive factors on multivariate analysis. Eighty five percent of the PALNs ≥11mm with heterogeneous internal density were pathologically metastatic, whereas 94.1% without them were not metastatic. PET had an accuracy, sensitivity, and specificity of 85.7%, 66.7%, and 94.1%, respectively. In patients with PALNs <11mm without heterogeneous internal density, the accuracy and specificity of PET improved to 93.8% and 96.6%, respectively. Conversely, in patients with some predictive CT findings, although the positive predictive value of PET increased from 83.3% to 88.9%, the accuracy and sensitivity remained at 70.6% and 66.7%, respectively, and 50.0% were false-negatives. CT had high NPV and relatively high PPV. PET had high specificity but low sensitivity. The addition of PET could be useful to confirm no PALN metastasis in patients with no predictive CT findings. Conversely, the improvement of diagnostic ability was limited in patients with some predictive CT findings.