Pancreatic Neuroendocrine Tumors in patients with Multiple Endocrine Neoplasia Type 1: Diagnostic Value of Different MRI Sequences

Background: Magnetic Resonance Imaging (MRI) is a useful imaging modality to assess the presence of Pancreatic Neuroendocrine Tumors (PNETs), allowing repeat monitoring examinations in MEN-1 patients. Objectives: We aimed to compare the diagnostic accuracy of conventional MRI sequences identifying which better depict the presence of PNETs in MEN-1 patients. Method: We performed a retrospective analysis of consecutive MEN-1 patients who underwent a conventional MRI protocol to monitor previously proven PNETs. MRI sequences T1-w Chemical-Shift (CS), T2-w HASTE, fat-suppressed (FS) T2-w HASTE, Diffusion Weighted Imaging (DWI), pre- and post-contrast FS T1-w sequences were independently analyzed by two experienced radiologists using a three-grade score (no lesion, uncertain lesion, certain lesion); lesion size and signal intensity were recorded. ANOVA Friedman and a Wilcoxon pairwise tests for the post-hoc analysis were used. The sensitivity of each sequence was measured; the results were analyzed with the Chi-squared test. Results: We included 21 patients with a total of 45 PNETs proven by histology, EUS guided fine needle aspiration, CT and nuclear medicine studies. A statistically significant (p<0.01) difference was observed in the detection performance of each MRI sequence, particularly between both DWI (91%) and T2-w FS (85%) sequences in comparison to the others (T1-w CS, T2-w, pre- and post-contrast FS T1-w, <=56% for all); no significant (p=0.5) difference was found between the detection performance of DWI and T2-w FS sequences. No correlation was observed between the qualitative score of each sequence and lesion tumor size. Conclusions: DWI and T2-w FS sequences proved to be the most accurate in the detection of PNETs, thus suggesting a role for an abbreviated MRI protocol without contrast medium administration for monitoring MEN-1 patients.