Comparison of conventional and 3-dimensional computed tomography against histopathologic examination in determining pancreatic adenocarcinoma tumor size: implications for radiation therapy planning

Abstract

Background and purpose: This study seeks to: (a) quantify radiologic-pathologic discrepancy for pancreatic adenocarcinoma by comparing tumor size on conventional computed tomography (C-CT) and 3-dimensional CT (3D-CT) to corresponding pathologic specimens; and (b) to identify clinico-pathologic characteristics predictive of radiologic-pathologic discrepancy to assist radiotherapy planning.

Materials and methods: Sixty-three patients with pancreatic adenocarcinoma and preoperative C-CT and volume-rendered 3D-CT imaging within 6 weeks of resection were identified. Maximum tumor diameter (MTD) was measured on pathology, C-CT, and 3D-CT and compared for each patient as well as among different clinico-pathologic subgroups.

Results: There was a trend toward C-CT underestimation of MTD compared to final pathology (p=0.08), but no significant difference between 3D-CT MTD and pathology (p=0.54). Pathologic tumor size was significantly underestimated by C-CT in patients with larger pathologic tumor size (>3.0 cm, p=0.0001), smaller tumor size on C-CT (<3.0 cm, p=0.003), higher CA19-9 (>90 U/mL, p=0.008), and location in the pancreatic head (p=0.015). A model for predicting pathologic MTD using C-CT MTD and CA19-9 level was generated.

Conclusions: 3D-CT may allow for more accurate contouring of pancreatic tumors than C-CT. Patients with the above clinico-pathologic characteristics may require expanded margins relative to tumor size estimates on C-CT during radiotherapy planning.

Fig. 1

A pancreatic adenocarcinoma from our series has a maximum tumor diameter (MTD) on (a) axial conventional computed tomography of 4.93 cm, while (b) coronal reconstruction on volume rendered 3-dimensional computed tomography reveals a greater MTD of 6.03 cm.

Fig. 2

Our model for predicting pathologic MTD (solid line) is plotted against actual pathologic MTD and C-CT MTD of our patients (dots). Tumors and predictive model are grouped by CA19-9 level >90 U/mL or ≤90 U/mL. Dashed line represents 1:1 correlation. MTD, maximum tumor diameter; C-CT, conventional CT; Path, pathology.