Calcifications and Cystic Morphology on Preoperative Imaging Predict Survival After Resection of Pancreatic Neuroendocrine Tumors

Background: Radiographic calcifications and cystic morphology are associated with higher and lower tumor grade, respectively, in pancreatic neuroendocrine tumors (PNETs). Whether calcifications and/or cystic morphology could be used preoperatively to predict post-resection survival in patients with PNETs remains elusive. Methods: Patients undergoing curative-intent resection of well-differentiated PNETs from 2000 to 2017 at eight academic institutions participating in the US Neuroendocrine Tumor Study Group were identified. Preoperative cross-sectional imaging reports were reviewed to identify the presence of calcifications and of a cystic component occupying >50% of the total tumor area. Clinicopathologic characteristics and recurrence-free survival (RFS) were compared. Results: Of 981 patients studied, 18% had calcifications and 17% had cystic tumors. Tumors with calcifications were more commonly associated with Ki-67 ≥3% (47% vs. 33%; p = 0.029), lymph node metastasis (36% vs. 24%; p = 0.011), and distant metastasis (13% vs. 4%; p < 0.001). In contrast, cystic tumors were less commonly associated with lymph node metastasis (12% vs. 30%; p < 0.001). Five-year RFS after resection was most favorable for cystic tumors without calcifications (91%), intermediate for solid tumors without calcifications (77%), and least favorable for any calcified PNET (solid 69%, cystic 67%; p = 0.043). Calcifications remained an independent predictor of RFS on multivariable analysis (p = 0.043) controlling for nodal (p < 0.001) and distant metastasis (p = 0.001). Conclusions: Easily detectable radiographic features, such as calcifications and cystic morphology, can be used preoperatively to stratify prognosis in patients with PNETs and possibly inform the decision to operate or not, as well as guide the extent of resection and potential use of neoadjuvant therapy.