Expression of metastasis-associated gene products and liver metastases in pancreatic endocrine tumors

Abstract

11089 Background: Outcomes in well-differentiated pancreatic endocrine tumors can be difficult to predict using pathologic criteria. We recently identified a novel set of 3 metastasis-associated genes by microarray: Palladin, p21, RUNX1T1. Our aim was to evaluate the potential for these markers, individually or in combination, to predict liver metastases as an indicator of adverse outcome. Methods: Palladin, p21, and RUNX1T1 immunostains were done on a tissue microarray of 39 resected primary pancreatic endocrine neoplasms, 14 of which had hepatic metastases. The Allred score was determined as the sum of stain intensity (scored 0–3) and % cells stained (scored 0–5). Receiver operating characteristic (ROC) analysis was used to choose the cutpoint in Allred score (high vs low protein expression) to optimize sensitivity and specificity for predicting liver metastases. Results: Nearly all tumors with liver metastases showed high Palladin and p21 levels (Allred score > 3 and > 4, respectively), while protein expression was lower in the majority of non-metastatic tumors. In contrast, RUNX1T1 expression was low (Allred score < 4) in most tumors with liver metastases, but higher in all except one of the non-metastatic tumors. Individual test sensitivities for predicting liver metastases were 100% for high Palladin, 93% for high p21 and 85% for low RUNX1T1, while corresponding specificities were 63%, 75%, and 96%. Tumors were correctly classified as being metastatic or not (predictive accuracy) by Palladin, p21, or RUNX1T1 expression in 76%, 76%, and 92% of cases, respectively. If abnormal expression of even one of 3 proteins is considered a positive test (parallel testing), then sensitivity of all 3 together for predicting liver metastases was 100%, specificity 48%, and predictive accuracy 68%. Conclusions: 1) High Palladin, high p21, or low RUNX1T1 expression have good sensitivity and specificity for predicting liver metastases in pancreatic endocrine tumors. 2) Parallel testing with all 3 markers achieved 100% sensitivity but at a cost of reduced specificity. 3) Differential expression of these biomarkers may predict aggressive tumor behavior that warrants more aggressive management. No significant financial relationships to disclose.