Threshold of Main Pancreatic Duct Diameter in Identifying Malignant Intraductal Papillary Mucinous Neoplasm by Magnetic Resonance Imaging

Abstract

Objective: Intraductal papillary mucinous neoplasm (IPMN) is a rare pancreatic lesion. The identification of malignancy is critical for the establishment of treatment strategies. Main pancreatic duct (MPD) diameter is one critical feature for malignant IPMNs. However, the threshold of 1.0 cm is challenged. In this study, we explored independent risk factors and further calculated the threshold of MPD in identifying malignant IPMNs. Method: A total of 151 IPMN patients were included in this retrospective study. Demographic information, clinicopathological features, laboratory testing, and preoperative radiological characteristics by magnetic resonance imaging were collected. The receiver operating characteristic (ROC) curves were performed to determine the MPD diameter's cutoff levels and evaluate the predicted factors' diagnostic ability. Results: A cutoff value of 0.77 cm MPD (an area under the curve (AUC) = 0.746) in all IPMNs and 0.82 cm (AUC = 0.742) in the main duct involved IPMNs was obtained. MPD diameter (odds ratio (OR), 12.67; 95% confidence interval (CI), 4.80-33.48) and the mural nodule (OR, 12.98; 95% CI, 3.18-52.97) were the independent associated factors with high-risk IPMNs. The combined model with MPD and mural nodule showed a better predictive performance than mural nodule or MPD diameter alone (AUC = 0.803 vs 0.619, 0.746). A nomogram was developed and showed good performance (C index = 0.803). Conclusion: Our data show that mural nodule and MPD diameter are independent risk factors in identifying malignant intraductal papillary mucinous neoplasms. A cutoff value of 0.77 cm of MPD diameter may be a threshold value in identifying malignant intraductal papillary mucinous neoplasms or undergoing surgical resection.

Keywords: intraductal papillary mucinous neoplasm; main pancreatic duct; mural nodule; risk factor; threshold.

Figure 1.

The scatter plots of MPD diameter in the different subsets of IPMNs. (A) The MPD diameter of low-risk and high-risk groups in all types of IPMN. (B) The MPD diameter of low-risk and high-risk groups in MD-/MTIPMN. (C) The MPD diameter of low-risk and high-risk groups in BD-IPMNs. **P < .01, ****P < .0001.

Figure 2.

Performance of the risk factors in predicting the high-risk IPMNs using ROC analysis. (A) Diagnostic values of MPD diameter (continuous data) for all type IPMNs and MD-/MT-IPMNs; (B) Diagnostic values of MPD diameter with different cutoff values (1.0 cm, 0.5 cm, and 0.77 cm) for high-risk lesions in all type IPMNs; (C) Diagnostic values of MPD diameter with different cutoff values (1.0 cm, 0.5 cm, and 0.82 cm) for high-risk lesions in MD-/MT-IPMNs; (D) Diagnostic values of the MPD diameter, mural nodule, and the combination model for high-risk lesions in all type IPMNs.

Figure 3.

Clinical nomograms for predicting high-risk lesions in all type IPMNs. (A) The model includes two variables in the nomogram: the mural nodule and MPD diameter (cutoff = 0.77 cm). (B) Calibration curve of the nomogram for predicting high-risk lesions in all type IPMNs.