Differentiation of pancreatic neuroendocrine tumors from pancreas renal cell carcinoma metastases on CT using qualitative and quantitative features

PurposeTo assess qualitative and quantitative imaging features on enhanced CT that may differentiate pancreatic neuroendocrine tumors (PNETs) from pancreatic renal cell carcinoma (RCC) metastases.MethodsThis IRB-approved multi-center retrospective case-control study compared 43 resected PNETs and 28 resected RCC metastases with pre-operative enhanced CT identified consecutively between 2003 and 2017. Two blinded radiologists (R1/R2) independently assessed tumor location, attenuation (relative to pancreas), composition (solid/cystic/mixed), homogeneity (homogeneous/heterogeneous), calcification, multiplicity, and for main pancreatic duct (MPD) dilation. Tumors were segmented for quantitative texture analysis. Data were analyzed with Chi square, logistic regression, and receiver operating characteristic (ROC). Inter-observer agreement was assessed (Cohen's kappa).ResultsThere was no difference in age, gender, location, attenuation, or composition (P>0.05) between groups. PNETs were larger than RCC metastases (3723mm vs. 26 +/- 21mm, P=0.038), more frequently solitary (P<0.001), subjectively more heterogeneous (P=0.033/0.144, R1/R2), and associated with calcification (P=0.002/0.004) and MPD dilation (P=0.025/0.006). Agreement for subjective features was moderate-to-almost perfect (K=0.4879-0.9481). Quantitative texture analysis showed higher entropy in PNETs (6.32 +/- 0.49 versus 5.96 +/- 0.53; P=0.004) with no difference in other features studied (P>0.05). Entropy had ROC area under the curve for diagnosis of PNET of 0.77 +/- 0.06, with optimal sensitivity/specificity of 71.4/79.1%.ConclusionsCompared to pancreatic RCC metastases, PNETs are larger, more frequently solitary, contain calcification, show MPD dilation, and are subjectively and quantitatively more heterogeneous tumors.