Pancreatic adenocarcinoma: quantitative CT features are correlated with fibrous stromal fraction and help predict outcome after resection.

Objectives: To identify quantitative imaging features of contrast-enhanced computed tomography (CE-CT) that may be prognostically favorable after resection of smaller (≤ 30 mm) pancreatic ductal adenocarcinomas (PDACs) located at head.

Methods: This retrospective study included two independent cohorts (discovery cohort, n = 212; test cohort, n = 100) of patients who underwent resection of head PDACs ≤ 30 mm and preoperative CE-CT. We examined tumor and surrounding parenchymal attenuation differences (deltas), and tumor attenuation changes across phases (ratios). Semantic features of PDACs were evaluated by two radiologists. Clinicopathologic and imaging features for predicting disease-free survival (DFS) and overall survival (OS) were analyzed via multivariate Lasso-penalized Cox proportional-hazards models. Survival rates were derived by Kaplan-Meier method.

Results: Imaging features achieved C-indices of 0.766 (discovery cohort) and 0.739 (test cohort) for DFS, and 0.790 (discovery cohort) and 0.772 (test cohort) for OS estimates through incorporation of clinicopathologic features. The most decisive imaging feature was delta 3, denoting attenuation differences between tumor and surrounding pancreas at pancreatic phase (DFS: HR = 2.122; OS: HR = 2.375; both p < 0.001). Compared with inconspicuous (low-delta-3, < 28 HU) tumors, conspicuous (high-delta-3) tumors correlated significantly with more aggressive histologic grades (p = 0.014) and less extensive tumor fibrous stromal fractions (p < 0.001). Patients with low-delta-3 tumors ≤ 20 mm experienced the most favorable outcomes (DFS, 36 months; OS, 42 months), whereas those with high-delta-3 tumors fared poorly, regardless of tumor size (DFS, 12 months; OS, 19 months).

Conclusions: Quantifiable CT imaging features reflect heterogeneous fibrous stromal fractions and histologic grades of PDAC at head locations that help stratify patients with disparate clinical outcomes.

Key Points: • Quantitative and semantic imaging features achieved promising results for the prognosis of resected PDAC (≤ 30 mm) at head location, through incorporation of clinicopathologic features. • Attenuation difference at tumor-parenchyma interface (delta 3) emerged as the most decisive imaging feature, enabling further stratification of patients into distinct prognostic subtypes by tumor size. • High delta 3 signifies sharper contrast between tumor and surrounding pancreas, correlating with more aggressive histologic grades and less extensive tumor fibrous stromal fractions.