e15693 Background: Resection of the primary tumor in metastatic neuroendocrine tumor (NET) is controversial. The aim of this study is to evaluate survival outcomes and identify prognostic variables of surgical resection of the primary tumor in metastatic NET patients. Methods: Data were obtained from all US hospitals that contributed to the National Cancer Database (NCDB) between 2004 and 2013. Chi-square and ANOVA tests were done to identify factors associated with surgical modality. Univariate and multivariate cox proportional hazards models were used for association between patient characteristics and survival. Kaplan-Meier curves were generated and log-rank tests conducted to compare the survival difference of patient characteristics. Results: A total of 2,361 patients between 18 and 90 years of age with stage IV well/intermediate-differentiated NET were identified. The mean age was 62.1 years (SD±13), with an equal male to female ratio (50.0%). Majority of NET primaries were in the small intestine (33.0%), pancreas (26.3%), and lung (24.4%). The majority were well differentiated tumors (69.6%) and 42.5% of patients underwent surgery at the primary site. On multivariate analysis total surgical resection of the primary (HR 0.44; 0.22-0.90; p < 0.001), female sex, year of diagnosis 2010-2014, negative surgical margin, Charlson-Deyo score < 2, and age < 51 years at diagnosis were associated with better overall survival (OS). Conclusions: Resection of the primary in stage IV well/intermediate-differentiated NET was associated with improved 5-year OS compared to patients with no surgery in small intestine (60.1% vs 44.2%), lung (70.0% vs 20.2%), and pancreas tumors (59.3% vs 30.6%).

795 Background: Clinico-pathological high risk features are frequently utilized in adjuvant chemotherapy (AC) decisions in stage II colorectal cancer and their utility in stage II appendiceal adenocarcinoma (AA) is less established. The aim of this study is to determine the impact of high risk features on clinical outcomes and whether high risk features are predictive of AC benefit in stage II AA. Methods: Patients with pathological stage II AA between 2010 and 2015 were identified from the National Cancer Database (NCDB) using ICD-O-3 morphology and topography codes: 8140, 8480 and C18.1. High risk stage II AA was defined as having at least one of the following clinicopathological features: T4 tumor, < 12 lymph nodes examined, poorly differentiated histology, positive margins, or lymphovascular invasion. Patients with none of these features were defined as low-risk. Results: A total of 1,040 patients were identified. 51.0% males, 84.5% Caucasian; median age 61 (range, 19-90). 46.4% were determined to have high-risk stage II AA. High-risk status was associated with worse OS compared to low-risk in univariate (HR 1.55; 95% CI 1.18-2.02; p = 0.001) and multivariable analyses (HR 1.36; 95% CI 1.03-1.79; p = 0.028). High-risk stage II AA patients had significantly worse 5-year OS compared to low-risk patients (67.1% vs. 74.5%, p = 0.0013). AC was administered in 34.4% (n = 166) of high-risk patients and in 36.5% (n = 203) of low-risk patients. Among high-risk patients, AC was not associated with better OS in univariate (HR 0.86; 95% CI 0.59-1.26; p = 0.722) and multivariable analyses (HR 1.35; 95% CI 0.90-2.04; p = 0.324) compared to no AC. Similarly, among low-risk patients, AC was not associated with better OS in univariate (HR 0.92; 95% CI 0.60-1.39; p = 0.813) and multivariable analyses (HR 1.27; 95% CI 0.81-2.02; p = 0.334) compared to no AC. For high-risk patients, 5-year OS was 68.3% in patients that received AC vs. 66.5% in patients that did not (p = 0.722). For low-risk patients, 5-year OS was 74.0% in patients that received AC vs. 76.3% in patients that did not (p = 0.813). Conclusions: High-risk stage II AA patients had significantly worse 5-year OS compared to low-risk patients. AC did not improve survival regardless of high risk features in stage II AA.

e16259 Background: Colloid carcinoma (CC) of the pancreas is a rare histopathological subtype of ductal adenocarcinoma (PDAC), with poorly defined prognostic factors and therapeutic outcomes. The aim of this study is to characterize the clinicopathological features and evaluate the overall survival (OS) and prognostic factors of patients with pancreatic CC using National Cancer Database (NCDB). Methods: Patients diagnosed with CC of the pancreas and PDAC between 2004 and 2016 were identified from the NCDB using ICD-O-3 morphology (8480/3 for CC and 8140/3 for PDAC) and topography codes (C25). Univariate and multivariable analyses were conducted and Kaplan-Meier analysis and Cox proportional hazards models were used to perform OS analysis. Results: A total of 56,846 patients met the inclusion criteria for the final analysis. Of the total population included, 2,430 patients (4.3%) had CC and 54,416 patients (95.7%) had PDAC. For both, CC and PDAC, there was a male preponderance (52.0%, 52.5%), Caucasians (85.1%, 84%), occurrence above the age of 70 (39.2%, 38.2%), and the most common primary site was the head of the pancreas (50.5%, 53%). For CC, the percentage of pathologic stage III colloid pancreas cancer appeared the lowest (3.5%, 85 patients), compared to stage I (16.7%), stage II (37.8%), and stage IV (42.1%). While in PDAC, the percentage of pathologic stage I (5.94%) and stage III (4.44%) patients was lower than stage II (37.21%) and IV (52.41%). CC and PDAC more frequently presented with < 5cm tumor, at academic or research cancer centers, and diagnosed between 2009 and 2013 compared to 2004–2008 ( p< 0.001). For both CC and PDAC, the majority underwent surgical resection (58%, 53%), systemic chemotherapy (57.8%, 63%) and did not receive radiotherapy (78.8%, 77.6%). A positive surgical margin on pathologic evaluation was associated with worse outcomes for CC and PDAC in both univariate and multivariate analysis (HR 1.61; 1.56–1.66; p< 0.001 and HR 1.43; 1.38–1.48, p< 0.001). CC had a better 1-year overall survival (OS) in all stages compared to PDAC (p < 0.001). In multivariate analysis, mucinous carcinoma histology, female sex, diagnosis between 2004 and 2009, well/moderately differentiated histology, chemotherapy, age at diagnosis less than 60, radiation therapy after surgery, and local surgical procedure of primary site and pancreatectomy (p < 0.001) were associated with better OS compared to PDAC. Colloid histology was associated with better 1-year overall survival (OS) in all stages compared to PDAC (p < 0.001). Conclusions: Colloid carcinoma of pancreas is associated with a better overall survival as compared to pancreatic ductal adenocarcinoma. This is the largest study to address the clinical features and outcomes of colloid carcinoma of pancreas.