CT-detected “acute-angle sign” of para-aortic lymph nodes as a prognostic biomarker in stage III colon cancer

To evaluate the prognostic value of a novel CT imaging feature, the Acute-Angle Sign (AAS), of para-aortic lymph nodes (PALNs) in stage III colon cancer. This retrospective study included patients with pathologically confirmed stage III colon cancer who underwent preoperative contrast-enhanced CT (2015-2019). The AAS was defined as any para-aortic lymph node with a short-axis diameter ≥8 mm exhibiting a sharp acute angle in any plane of the axial, coronal, or sagittal views. Progression-free survival (PFS) and overall survival (OS) were evaluated using Kaplan–Meier analysis and Cox regression. Interobserver agreement was assessed using Fleiss’ κ. A total of 417 patients were included (mean age, 60 ± 11 years [SD]; 225 males). The AAS was identified in 21 patients (5%). After a median follow-up of 78 months, disease progression occurred in 52% of AAS-positive patients compared with 33% of AAS-negative patients. In multivariable analysis, AAS (HR, 2.02; 95% CI: 1.05, 3.91), CEA (HR, 1.56; 95% CI: 1.11, 2.20), pT stage, and c-Met expression were independent predictors of 5-year PFS. Subgroup analysis showed that AAS was associated with poorer prognosis in patients with PALN enlargement ( P = 0.04), receiving adjuvant therapy ( P = 0.03), with left-sided tumors ( P = 0.006), and with c-Met positivity ( P = 0.005). Interobserver agreement for AAS was good (κ = 0.77). The Acute-Angle Sign (AAS) of para-aortic lymph nodes on CT is a reproducible imaging biomarker that independently predicts poor prognosis in patients with stage III, left-sided colon cancer.