A pilot study of radiologic measures of abdominal adiposity: weighty contributors to early pancreatic carcinogenesis worth evaluating?

Abstract

Objective: Intra-abdominal fat is a risk factor for pancreatic cancer (PC), but little is known about its contribution to PC precursors known as intraductal papillary mucinous neoplasms (IPMNs). Our goal was to evaluate quantitative radiologic measures of abdominal/visceral obesity as possible diagnostic markers of IPMN severity/pathology.

Methods: In a cohort of 34 surgically-resected, pathologically-confirmed IPMNs (17 benign; 17 malignant) with preoperative abdominal computed tomography (CT) images, we calculated body mass index (BMI) and four radiologic measures of obesity: total abdominal fat (TAF) area, visceral fat area (VFA), subcutaneous fat area (SFA), and visceral to subcutaneous fat ratio (V/S). Measures were compared between groups using Wilcoxon two-sample exact tests and other metrics.

Results: Mean BMI for individuals with malignant IPMNs (28.9 kg/m²) was higher than mean BMI for those with benign IPMNs (25.8 kg/m²) (P=0.045). Mean VFA was higher for patients with malignant IPMNs (199.3 cm²) compared to benign IPMNs (120.4 cm²),P=0.092. V/S was significantly higher (P=0.013) for patients with malignant versus benign IPMNs (1.25vs. 0.69 cm²), especially among females. The accuracy, sensitivity, specificity, and positive and negative predictive value of V/S in predicting malignant IPMN pathology were 74%, 71%, 76%, 75%, and 72%, respectively.

Conclusions: Preliminary findings suggest measures of visceral fat from routine medical images may help predict IPMN pathology, acting as potential noninvasive diagnostic adjuncts for management and targets for intervention that may be more biologically-relevant than BMI. Further investigation of gender-specific associations in larger, prospective IPMN cohorts is warranted to validate and expand upon these observations.

Keywords: Abdominal obesity; computed tomography; pancreatic cancer; pre-malignant lesions.

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Axial post contrast CTs (A and B) and quantitative segmentation (C and D) for two representative side BD IPMN cases with main pancreatic ducts normal in caliber. Case 1 has a well-demarcated homogenous hypodense 4.8 cm cystic lesion in the pancreatic neck (yellow arrow). The cystic lesion abuts the gastroduodenal artery (red arrow) without definite encasement. Case 2 has a poorly defined 1.3 cm hypoenhancing pancreatic neck lesion (yellow arrow). C and D: (1) Axial CT image through L2–L3 intervertebral disc level. (2) Axial CT subtracted image at superior endplate of L3. Abdominal wall and paraspinal muscle area were segmented and thresholds set to voxels with Hounsfield units (HU) –29 to 150. Visceral fat, intra-abdominal organs, and vasculature were subtracted. Although skeletal muscle indices can be obtained in a complementary manner to visceral fat measurements, these were not directly analyzed in this study. (3) Total abdominal fat with HU thresholds applied to include fat density voxels with HU –249 to –49 (green). (4) Manual segmentation of visceral fat regions (green).