Calcifications and cystic morphology on preoperative imaging predict survival after resection of pancreatic neuroendocrine tumors

Abstract

Background: Previous studies have shown radiographic calcifications and cystic morphology in pancreatic neuroendocrine tumors (PNET) are associated with higher and lower grade, respectively. A correlation between these radiographic features and survival after resection has not been proven. We sought to investigate the prognostic significance of these morphologic features after PNET resection utilizing a large multi-institutional US dataset. Methods: Patients undergoing curative-intent resection of well-differentiated PNET from 2000 to 2017 at 8 academic institutions, participating at the US Neuroendocrine Tumor Study Group, were identified. Preoperative cross-sectional imaging (CT and/or MRI) was reviewed to classify patients according to 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 included in the study, 18% had calcifications and 17% were cystic. Median tumor size was larger for tumors with than without calcifications (3.2 vs. 2.0 cm, p = 0.001), but not for cystic vs. solid tumors (2.3 vs. 2.2 cm, p = 0.144). Tumors with calcifications were more commonly associated with Ki-67 3% (47% vs. 33%, p = 0.029) and lymph node metastasis (36% vs. 24%, p = 0.011). Cystic tumors were less commonly associated with lymph node metastasis (12% vs. 30%, p < 0.001). Calcifications and cystic morphology were associated with lower and higher RFS, respectively (Figure 1a,b), with cystic tumors without calcifications representing the most favorable group (Figure 1c). Conclusion: Easily detectable radiographic features, such as calcifications and cystic morphology, can be used preoperatively to stratify prognosis in patients with PNETs, possibly guiding the extent of resection or utilization of neoadjuvant therapy strategies.