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Completion lymph node dissection (CLND) was the standard treatment for patients with melanoma with positive sentinel lymph nodes (SLN) until 2017 when data from the DeCOG-SLT and MLST-2 randomized trials challenged the survival benefit of this procedure. We assessed the contribution of patient, tumor and facility factors on the use of CLND in patients with surgically resected Stage III melanoma.Using the National Cancer Database, patients who underwent surgical excision and were found to have a positive SLN from 2012 to 2017 were included. A multivariable mixed-effects logistic regression model with a random intercept for the facility was used to determine the effect of patient, tumor, and facility variables on the risk of CLND. Reference effect measures (REMs) were used to compare the contribution of contextual effects (unknown facility variables) versus measured variables on the variation in CLND use.From 2012 to 2017, the overall use of CLND decreased from 59.9% to 26.5% (p 0.0001). Overall, older patients and patients with government-based insurance were less likely to undergo CLND. Tumor factors associated with a decreased rate of CLND included primary tumor location on the lower limb, decreasing depth, and mitotic rate1. However, the contribution of contextual effects to the variation in CLND use exceeded that of the measured facility, tumor, time, and patient variables.There was a decrease in CLND use during the study period. However, there is still high variability in CLND use, mainly driven by unmeasured contextual effects.

ImportanceThe number of patients with small nonfunctional pancreatic neuroendocrine tumors (NF-PanNETs) is increasing. However, the role of surgery for small NF-PanNETs remains unclear.ObjectiveTo evaluate the association between surgical resection for NF-PanNETs measuring 2 cm or smaller and survival.Design, Setting, and ParticipantsThis cohort study used data from the National Cancer Database and included patients with NF-pancreatic neuroendocrine neoplasms who were diagnosed between January 1, 2004, and December 31, 2017. Patients with small NF-PanNETs were divided into 2 groups: group 1a (tumor size, ≤1 cm) and group 1b (tumor size, 1.1-2.0 cm). Patients without information on tumor size, overall survival, and surgical resection were excluded. Data analysis was performed in June 2022.ExposuresPatients with vs without surgical resection.Main Outcomes and MeasuresThe primary outcome was overall survival of patients in group 1a or group 1b who underwent surgical resection compared with those who did not, which was evaluated using Kaplan-Meier estimates and multivariable Cox proportional hazards regression models. Interactions between preoperative factors and surgical resection were analyzed with a multivariable Cox proportional hazards regression model.ResultsOf the 10 504 patients with localized NF-PanNETs identified, 4641 were analyzed. These patients had a mean (SD) age of 60.5 (12.7) years and included 2338 males (50.4%). The median (IQR) follow-up time was 47.1 (28.2-71.6) months. In total, 1278 patients were in group 1a and 3363 patients were in group 1b. The surgical resection rates were 82.0% in group 1a and 87.0% in group 1b. After adjustment for preoperative factors, surgical resection was associated with longer survival for patients in group 1b (hazard ratio [HR], 0.58; 95% CI, 0.42-0.80; P P = .12). In group 1b, interaction analysis found that age of 64 years or younger, absence of comorbidities, treatment at academic institutions, and distal pancreatic tumors were factors associated with increased survival after surgical resection.Conclusions and RelevanceFindings of this study support an association between surgical resection and increased survival in select patients with NF-PanNETs measuring 1.1 to 2.0 cm who were younger than 65 years, had no comorbidities, received treatment at academic institutions, and had tumors of the distal pancreas. Future investigations of surgical resection for small NF-PanNETs that include the Ki-67 index are warranted to validate these findings.

ImportanceThe total number of patients with pancreatic ductal adenocarcinoma (PDAC) who receive neoadjuvant chemotherapy (NAC) is increasing. However, the added role of adjuvant chemotherapy (AC) in these patients remains unknown.ObjectiveTo evaluate the association of AC with overall survival (OS) in patients with PDAC who received multiagent NAC followed by curative-intent surgery.Design, Setting, and ParticipantsThis retrospective, matched-cohort study used data from the National Cancer Database and included patients with PDAC diagnosed between 2010 and 2018. The study included patients at least 18 years of age who received multiagent NAC followed by surgical resection and had available records of the pathological findings. Patients were excluded if they had clinical or pathological stage IV disease or died within 90 days of their operation.ExposuresAll included patients received NAC and underwent resection for primary PDAC. Some patients received adjuvant chemotherapy.Main Outcomes and MeasuresThe main outcome was the OS of patients who received AC (AC group) vs those who did not (non-AC group). Interactions between pathological findings and AC were investigated in separate multivariable Cox regression models.ResultsIn total, 1132 patients (mean [SD] age, 63.5 [9.4] years; 577 [50.1%] male; 970 [85.7%] White) were included, 640 patients in the non-AC group and 492 patients in the AC group. After being matched by propensity score according to demographic and pathological characteristics, 444 patients remained in each group. The multivariable Cox regression model adjusted for all covariates revealed an association between AC and improved survival (hazard ratio, 0.71; 95% CI, 0.59-0.85; P P = .002), but the benefit varied by age, pathological T category, and tumor differentiation. Of note, AC was associated with better survival in patients with any pathological N category and positive margin status.Conclusions and RelevanceIn this cohort study, AC following multiagent NAC and resection in patients with PDAC was associated with significant survival benefit compared with that in patients who did not receive AC. These findings suggest that patients with aggressive tumors may benefit from AC to achieve prolonged survival, even after multiagent NAC and curative-intent resection.

Background: Current evidence on overall survival (OS) between invasive pancreatic ductal adenocarcinoma (PDAC) and intraductal papillary mucinous neoplasm (IPMN) is limited to single-center reports. We aimed to compare the characteristics, management, and OS of invasive PDAC vs. IPMN using a national United States (US) database. Methods: Invasive PDAC or IPMN adult (≥18 years) patients were identified in the National Cancer Database (2004–2016). OS was assessed with the Kaplan–Meier method and the stratified log-rank test. Results: We included 101,190 patients (100,834 PDAC, 356 IPMN). A higher proportion of PDAC vs. IPMN patients had clinical N1 (36.8% vs. 15.7%, p < 0.001) and M1 disease (41.2% vs. 5.9%, p < 0.001). A lower proportion of PDAC patients underwent surgery (25.5% vs. 80.3%, p < 0.001), but a higher proportion received chemotherapy (65.4% vs. 46.1%, p < 0.001) or radiation (25.3% vs. 20.5%, p = 0.04). A higher proportion of surgical patients with PDAC vs. IPMN underwent margin-positive resection (23.0% vs. 14.0%, p = 0.001). The median OS for PDAC vs. IPMN was 8.3 vs. 33.4 months. In the stratified analysis for N0M0 disease, the median OS for PDAC vs. IPMN was 12.8 vs. 43.3 months, for N1M0, it was 11.5 vs. 17.0 months, while for M1, it was 4.0 vs. 7.0 months. In both diagnoses, surgery yielded improved OS, while stratified analysis in the surgical cohort demonstrated similar findings. Conclusions: Invasive PDAC is more aggressive than invasive IPMN, yet in the case of metastasis, OS is equally poor. Excellent long-term OS is achievable with surgical resection in highly selected cases, and efforts should focus on facilitating surgical treatment.

722 Background: While neoadjuvant chemotherapy is increasingly being using in pancreatic cancer treatment, it is unclear whether it is beneficial in treatment of body and tail tumors. Randomized controlled trials are lacking and previous observational studies have not demonstrated any benefit. We aimed to assess survival associations, trends over time and patient selection associations for multiagent neoadjuvant chemotherapy treated pancreatic cancer of the body and tail using data from the National Cancer Database (NCDB). Methods: We queried the NCDB for pancreatic adenocarcinoma in the body or tail diagnosed between 2010 – 2018 that received multiagent neoadjuvant chemotherapy and/or a distal pancreatectomy. Patients with clinical M1, clinical T4 and surgery other than partial pancreatectomy were excluded. Survival was compared with Kaplan-Meier estimates and multivariable Cox Proportional Hazard Estimates. Results: Between 2010 – 2018, the use of multiagent neoadjuvant chemotherapy increased from 5.7% to 31.8%. In total, 1951 patients were included with n = 384 receiving multiagent neoadjuvant chemotherapy (cases) and n = 1567 undergoing upfront surgery (controls). Neoadjuvant chemotherapy was associated with younger age, tumor in the pancreatic body, clinical N1-2 and with Ca 19-9 ≥98 U/mL. Neoadjuvant chemotherapy was associated with a decreased mortality rate in multivariable Cox regression models adjusting for preoperatively assessed variables (HR 0.65, 95% CI 0.53 – 0.81, p < 0.001) and results were significant in both clinical T1-2 and T3 tumors. Patients treated with upfront surgery had higher rates of adjuvant chemotherapy receipt after resection (41.4% vs 70.6%) but there was no difference in R1 resection rates or 90-day postoperative mortality between the groups. The addition of neoadjuvant radiotherapy was not associated with improved survival in patients receiving neoadjuvant chemotherapy. Conclusions: Multiagent neoadjuvant chemotherapy is increasingly being used in the treatment of pancreatic cancer of the body and tail, especially in younger patients and patients with more aggressive tumor characteristics. Multiagent neoadjuvant chemotherapy is associated with improved survival but randomized trials are needed to establish causal relationships.

238 Background: Appendiceal neuroendocrine tumors (ANETs) are well known for their benign and slow progression; nonetheless, the presence of lymph node metastasis has been described in up to 50% of all cases. The risk of metastasis is mainly associated with tumor size, and the role of other pathological features remains unclear. Hence, this study was designed to assess the pathologic features of ANETs associated with an increased risk of lymph node metastasis. Methods: Patients ≥18yrs of age with ANETs were identified in the National Cancer Database (NCDB) from 2004 to 2017. Groups were defined based on lymph node status as N(-) (all examined nodes were negative) and N(+) (one or more examined nodes were positive). Multivariable models using demographics and oncological features were used to identify factors independently associated with nodal metastasis (N+). Marginal effects, specifically for tumors

645 Background: The role of surgery for small (≤2 cm), nonfunctional pancreatic neuroendocrine tumors (NF-PNETs) remains controversial due to the wide range of tumor aggressiveness. Consensus guidelines of the US, Europe, and Japan offer different recommendations for treatment of small NF-PNETs. The objective of this study is to evaluate the survival benefit of surgical resection for small NF-PNETs. Methods: Patients with NF-PNETs were identified in the National Cancer Database from 2004 to 2018. Small NF-PNETs were divided into two groups: group 1a (tumor ≤1 cm) and group 1b (tumor 1.1 – 2.0 cm). Cox regression models were used to compare the overall survival between resected and unresected small NF-PNETs patients. Interactions between preoperative factors and surgery were estimated using subgroup analyses. Results: We identified 1,278 patients in group 1a and 3,363 patients in group 1b. After adjusting for preoperative factors, surgery was associated with longer survival for patients in group 1b (HR, 0.58; 95% CI, 0.42–0.80; P

Simple Summary Intraductal papillary mucinous neoplasms (IPMN) are common but difficult to manage since accurate tools for diagnosing malignancy are unavailable. This study evaluates the diagnostic value of main pancreatic duct (MPD) diameter for detecting IPMN malignancy, using a meta-analysis of published data. The result suggests that malignancy is highly prevalent in IPMN with ductal dilatation of >5 mm. Abstract Intraductal papillary mucinous neoplasms (IPMN) are common but difficult to manage since accurate tools for diagnosing malignancy are unavailable. This study tests the diagnostic value of the main pancreatic duct (MPD) diameter for detecting IPMN malignancy using a meta-analysis of published data of resected IPMNs. Collected from a comprehensive literature search, the articles included in this analysis must report malignancy cases (high-grade dysplasia (HGD) and invasive carcinoma (IC)) and MPD diameter so that two MPD cut-offs could be created. The sensitivity, specificity, and odds ratios of the two cutoffs for predicting malignancy were calculated. A review of 1493 articles yielded 20 retrospective studies with 3982 resected cases. A cutoff of ≥5 mm is more sensitive than the ≥10 mm cutoff and has pooled sensitivity of 72.20% and 75.60% for classification of HGD and IC, respectively. Both MPD cutoffs of ≥5 mm and ≥10 mm were associated with malignancy (OR = 4.36 (95% CI: 2.82, 6.75) vs. OR = 3.18 (95% CI: 2.25, 4.49), respectively). The odds of HGD and IC for patients with MPD ≥5 mm were 5.66 (95% CI: 3.02, 10.62) and 7.40 (95% CI: 4.95, 11.06), respectively. OR of HGD and IC for MPD ≥10 mm cutoff were 4.36 (95% CI: 3.20, 5.93) and 4.75 (95% CI: 2.39, 9.45), respectively. IPMN with MPD of >5 mm could very likely be malignant. In selected IPMN patients, pancreatectomy should be considered when MPD is >5 mm.