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OBJECTIVE: To evaluate whether pathologic complete response (pCR) exclusively defines major pathologic response to treatment with improved survival. SUMMARY BACKGROUND DATA: pCR following trimodality therapy for esophagogastric adenocarcinoma is infrequent but associated with improved prognosis. Yet most clinical trials and correlative studies designate pCR as the primary endpoint. METHODS: We analyzed our prospectively maintained database for patients who underwent trimodality therapy for locally advanced esophageal adenocarcinoma between 1995 and 2017. Overall survival (OS) was examined by percentage treatment response (TR) in the primary tumor bed and pathologic nodal stage (ypN0) using Kaplan-Meier plots. Optimal thresholds of TR for differentiating patients in terms of OS were investigated with descriptive plots using restricted cubic spline functions; associations were quantified using Cox multivariable analysis. RESULTS: Among 788 patients, median follow-up was 37.5 months (range, 0.4–210.6); median OS was 48.3 months (95% CI, 42.2–58.8). Absence of residual nodal disease was independently associated with improved survival (P

Objective: We sought to define criteria associated with low lymph node metastasis risk in patients with submucosal (pT1b) gastric cancer from 3 Western and 3 Eastern countries. Summary Background Data: Accurate prediction of lymph node metastasis risk is essential when determining the need for gastrectomy with lymph node dissection following endoscopic resection. Under present guidelines, endoscopic resection is considered definitive treatment if submucosal invasion is only superficial, but this is not routinely assessed. Methods: Lymph node metastasis rates were determined for patient groups defined according to tumor pathological characteristics. Clinicopathological predictors of lymph node metastasis were determined by multivariable logistic regression and used to develop a nomogram in a randomly selected subset that was validated in the remainder. Overall survival was compared between Eastern and Western countries. Results: Lymph node metastasis was found in 701 of 3166 (22.1%) Eastern and 153 of 560 (27.3%) Western patients. Independent predictors of lymph node metastasis were female sex, tumor size, distal stomach location, lymphovascular invasion, and moderate or poor differentiation. Patients fulfilling the National Comprehensive Cancer Network guideline criteria, excluding the requirement that invasion not extend beyond the superficial submucosa, had a lymph node metastasis rate of 8.9% (53/594). Excluding moderately differentiated tumors lowered the rate to 3.4% (10/296). The nomogram's area under the curve was 0.690. Regardless of lymph node status, overall survival was better in Eastern patients. Conclusions: The lymph node metastasis rate was lowest in patients with well differentiated tumors that were 3 cm and lacked lymphovascular invasion. These criteria may be useful in decisions regarding endoscopic resection as definitive treatment for pT1b gastric cancer.

Aim: Data are limited on PD-L1 expression and its association with overall survival (OS) in gastric cancer (GC) patients receiving routine care in different regions. Materials & methods: In a retrospective study, PD-L1 expression was assayed using the 22C3 pharmDx on GC tumor samples collected between 2003 and 2017 at South Korean and US cancer centers. PD-L1 positivity was defined as combined positive score (CPS) ≥1. The relationship between PD-L1 and OS was analyzed. Results: Of 574 GC tumor samples, 67.4% were CPS ≥1 (68.7% in Korean and 65.7% in US patients). PD-L1 expression was not associated with OS (adjusted hazard ratio: 0.94; 95% CI: 0.75–1.17). Conclusion: PD-L1 prevalence and its association with OS was similar between South Korean and US GC patients.

To evaluate the efficacy of chemotherapy in patients with microsatellite instability-high (MSI-high) gastric cancer.Although MSI-high gastric cancer is associated with superior prognosis, recent studies question the benefit of perioperative chemotherapy in this population.Locally advanced gastric adenocarcinoma patients who either underwent surgery alone or also received neoadjuvant, perioperative, or adjuvant chemotherapy between 2000-2018 were eligible. MSI status, determined by next generation sequencing or mismatch repair protein immunohistochemistry, was determined in 535 patients. Associations among MSI status, chemotherapy administration, and overall survival (OS), disease-specific survival (DSS), and disease-free survival (DFS) were assessed.In 535 patients, 82 (15.3%) had an MSI-high tumor and approximately 20% better OS, DSS, and DFS. Grade 1 (90-100%) pathological response to neoadjuvant chemotherapy was found in 0 of 40 (0%) MSI-high tumors versus 43 of 274 (16%) MSS. In the MSI-high group, the 3-year OS rate was 79% with chemotherapy versus 88% with surgery alone (P=0.48). In the MSS group, this was 61% versus 59%, respectively (P=0.96). After multivariable interaction analyses, patients with MSI-high tumors had superior survival compared with patients with MSS tumors whether given chemotherapy (HR 0.53, 95% CI 0.28-0.99) or treated with surgery alone (HR 0.15 vs. MSS, 95% CI 0.02-1.17).MSI-high locally advanced gastric cancer was associated with superior survival compared to MSS overall, despite worse pathological chemotherapy response. In patients with MSI-high gastric cancer who received chemotherapy, the survival rate was approximately 9% worse compared with surgery alone, but chemotherapy was not significantly associated with survival.

Supplementary Video from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Supplementary Data from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Nerves are a component of the tumor microenvironment contributing to cancer progression, but the role of cells from nerves in facilitating cancer invasion remains poorly understood. Here we show that Schwann cells (SC) activated by cancer cells collectively function as tumor-activated Schwann cell tracks (TAST) that promote cancer cell migration and invasion. Nonmyelinating SCs form TASTs and have cell gene expression signatures that correlate with diminished survival in patients with pancreatic ductal adenocarcinoma. In TASTs, dynamic SCs form tracks that serve as cancer pathways and apply forces on cancer cells to enhance cancer motility. These SCs are activated by c-Jun, analogous to their reprogramming during nerve repair. This study reveals a mechanism of cancer cell invasion that co-opts a wound repair process and exploits the ability of SCs to collectively organize into tracks. These findings establish a novel paradigm of how cancer cells spread and reveal therapeutic opportunities.Significance:How the tumor microenvironment participates in pancreatic cancer progression is not fully understood. Here, we show that SCs are activated by cancer cells and collectively organize into tracks that dynamically enable cancer invasion in a c-Jun–dependent manner.See related commentary by Amit and Maitra, p. 2240.This article is highlighted in the In This Issue feature, p. 2221

Supplementary Figure from Reprogrammed Schwann Cells Organize into Dynamic Tracks that Promote Pancreatic Cancer Invasion

Supplementary Data from The Role of the TP53 Pathway in Predicting Response to Neoadjuvant Therapy in Esophageal Adenocarcinoma

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Background: Mesothelin is overexpressed in several malignancies and is purportedly a specific marker of malignant transformation. In this pilot study, we investigated whether tissue and serum mesothelin are potential markers of neoplastic progression in Barrett's esophagus (BE) and in esophageal adenocarcinoma (EAC).Methods: Mesothelin expression was retrospectively evaluated in normal, BE, and EAC tissue from surgically resected esophageal specimens (n = 125). In addition, soluble mesothelin-related peptide (SMRP) levels were measured in serum.Results: Normal esophageal mucosa did not express mesothelin. BE tissue with high-grade dysplasia specifically expressed mesothelin, whereas BE tissue with low-grade or without dysplasia did not. Fifty-seven (46%) EAC tumors were positive for mesothelin. EAC tumors with BE expressed mesothelin more often than those without BE (58% vs. 35%, P = 0.01). SMRP levels were elevated in 70% of EAC patients (mean = 0.89 nmol/L; range: 0.03–3.77 nmol/L), but not in patients with acid reflux and/or BE.Conclusions: Mesothelin is commonly expressed in BE-associated EAC. On the basis of this pilot study, a prospective study is under way to evaluate tissue and serum mesothelin which are potential markers of neoplastic progression in BE and in EAC (NCT01393483).Impact: Current surveillance methods in Barrett's esophagus are invasive and neither cost-effective nor sensitive. This pilot study suggests that serum mesothelin is a marker of neoplastic transformation in BE and may provide a noninvasive method to improve identification of malignant transformation. Cancer Epidemiol Biomarkers Prev; 21(3); 482–6. ©2012 AACR.

LC gene signature classifier and gene list

TMA data for ASCL1 and S100 of 173 LCs

Differentially expressed genes between AC and TC of LC1

Purpose:In patients with locally advanced esophageal adenocarcinoma, response to neoadjuvant therapy strongly predicts survival, but robust molecular predictors of response have been lacking. We therefore sought to discover meaningful predictors of response in these patients.Experimental Design:We retrospectively identified all patients with adenocarcinoma of the lower esophagus or gastroesophageal junction who (i) were treated with multimodality therapy with curative intent at our institution from 2014 through 2020 and (ii) underwent prospective sequencing by Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets. Clinicopathologic and genomic data were analyzed to identify potential genomic features, somatic alterations, and oncogenic pathways associated with treatment response.Results:In total, 237 patients were included. MDM2 amplification was independently associated with poor response to neoadjuvant therapy [OR, 0.10 (95% confidence interval, 0.01–0.55); P = 0.032], when accounting for significant clinicopathologic variables, including clinical stage, tumor grade, and chemotherapy regimen. Moreover, TP53 pathway alterations, grouped according to inferred severity of TP53 dysfunction, were significantly associated with response to neoadjuvant therapy (P = 0.004, q = 0.07). Patients with MDM2 amplifications or truncating biallelic TP53 mutations had similar outcomes in terms of poor responses to neoadjuvant therapy and, consequently, shorter progression-free survival, compared with patients with TP53 pathway wild-type tumors. Thus, worsening TP53 dysfunction was directly correlated with worse outcomes.Conclusions:MDM2 amplification and TP53 status are associated with response to therapy in patients with esophageal adenocarcinoma. Given the dearth of actionable targets in esophageal adenocarcinoma, MDM2 inhibition, in combination with cytotoxic chemotherapy, may represent an important therapeutic strategy to overcome treatment resistance and improve outcomes in these patients.

Purpose:To delineate recurrent oncogenic driver alterations and dysregulated pathways in esophageal adenocarcinoma and to assess their prognostic value.Experimental Design:We analyzed a large cohort of patients with lower esophageal and junctional adenocarcinoma, prospectively sequenced by MSK-IMPACT with high-quality clinical annotation. Patients were subdivided according to treatment intent, curative versus palliative, which closely mirrored clinical staging. Genomic features, alterations, and pathways were examined for association with overall survival using Cox proportional hazard models, adjusted for relevant clinicopathologic factors knowable at the time of diagnosis.Results:Analysis of 487 patients revealed 16 oncogenic driver alterations, mostly amplifications, present in ≥5% of patients. Patients in the palliative-intent cohort, compared with those in the curative-intent cohort, were more likely to have metastatic disease, ERBB2 amplifications, Cell-cycle and RTK–RAS pathway alterations, as well as a higher fraction of genome altered and rate of whole-genome doubling. In multivariable analyses, CDKN2A alterations, SMAD4 alterations, KRAS amplifications, Cell-cycle and TGFβ pathways, and overall number of oncogenic drivers were independently associated with worse overall survival. ERBB2 amplification was associated with improved survival, presumably due to trastuzumab therapy.Conclusions:Our study suggests that higher levels of genomic instability are associated with more advanced disease in esophageal adenocarcinoma. Furthermore, CDKN2A, KRAS, and SMAD4 represent prognostic biomarkers, given their strong association with poor survival.

Supplementary Figure 1: Subtype LC2 specific MEN1 loss of heterozygosity. Supplementary Figure 2: PCA on gene expression for top variable number of genes. Supplementary Figure 3: Pearson correlation on top 3000 variable genes. Supplementary Figure 4: Heatmap of top 100 variable genes. Supplementary Figure 5: PCA of top variable number of CpG sites. Supplementary Figure 6: Boxplot of gene expression of HNF1A, FOXA3 and HNF4A across three LC subtypes. Supplementary Figure 7: Low expression of HOX family members in LC2 subtype. Supplementary Figure 8: Heatmap of LCs classifier from 30 LC dataset on independent lung carcinoids cohort from Fernandez-Cuesta et al. Supplementary Figure 9: Heatmap of HNF1A, FOX3 and FEV on Fernandez-Cuesta et al gene expression dataset. Supplementary Figure 10: Key targets of ASCL1 transcription factor. Supplementary Figure 11: Clinical features of three LC subtypes for median age of diagnosis. Supplementary Table1: Tumor purity scores for 30 LC samples using gene expression profile. Supplementary Table2: Significant Pathways/Gene Ontologies for top 100 variable genes. Supplementary Table3: Global methylation CpG count under hypo (beta =0.7) methylated probes for 18 LC samples. Supplementary Table4: IHC staining results for ASCL1 and S100 biomarker in 20 LC dataset

Differentially methylated CpG probes and CpG islands

Differentially expressed genes between three LC subtypes and pathway analysis

Alterations in esophageal adenocarcinoma in the TCGA dataset, and mapping of alterations onto the RTK-RAS and Cell Cycle pathways.

Supplementary Figure from The Role of the TP53 Pathway in Predicting Response to Neoadjuvant Therapy in Esophageal Adenocarcinoma

Supplementary Tables 1 and 2

Clinical characterization and tumor purity

Lung carcinoids (LC) are rare and slow growing primary lung neuroendocrine tumors. We performed targeted exome sequencing, mRNA sequencing, and DNA methylation array analysis on macro-dissected LCs. Recurrent mutations were enriched for genes involved in covalent histone modification/chromatin remodeling (34.5%; MEN1, ARID1A, KMT2C, and KMT2A) as well as DNA repair (17.2%) pathways. Unsupervised clustering and principle component analysis on gene expression and DNA methylation profiles showed three robust molecular subtypes (LC1, LC2, LC3) with distinct clinical features. MEN1 gene mutations were found to be exclusively enriched in the LC2 subtype. LC1 and LC3 subtypes were predominately found at peripheral and endobronchial lung, respectively. The LC3 subtype was diagnosed at a younger age than LC1 and LC2 subtypes. IHC staining of two biomarkers, ASCL1 and S100, sufficiently stratified the three subtypes. This molecular classification of LCs into three subtypes may facilitate understanding of their molecular mechanisms and improve diagnosis and clinical management.Significance:Integrative genomic analysis of lung carcinoids identifies three novel molecular subtypes with distinct clinical features and provides insight into their distinctive molecular signatures of tumorigenesis, diagnosis, and prognosis.

Purpose:Immune checkpoint inhibitors (ICI) are effective in only a minority of patients with esophagogastric cancer (EGC). Here, we aimed to identify predictors of durable clinical benefit to ICI in EGC.Experimental Design:Patients with advanced EGC treated with ICIs at Memorial Sloan Kettering Cancer Center (New York, NY) were identified. Clinicopathologic variables were assessed. In patients profiled by MSK-IMPACT–targeted sequencing, outcomes were correlated with tumor genomic features.Results:One-hundred sixty-one patients were treated with ICIs (110 with anti–PD-1/PD-L1 antibodies and 51 with anti–CTLA-4 and PD-1/PD-L1 antibodies). The median progression-free survival (PFS) and overall survival (OS) were 1.7 and 4.9 months, respectively. Greater number of disease sites (≥3), liver metastases, treatment with ≥3 prior therapies and ECOG performance status ≥2 were associated with poorer PFS and OS. Patients treated with combination ICI and those with PD-L1–positive tumors had improved outcomes. There was no difference in outcomes between patients treated with antibiotics during or in the 2 months preceding ICI treatment versus those who were not. Occurrence of irAEs was associated with improved OS. In genomically profiled tumors (n = 89), survival was associated with increasing tumor mutation burden (TMB). However, in multivariable analyses and when microsatellite unstable (MSI) patients were excluded, a significant association was no longer observed.Conclusions:In patients with advanced EGC, heavily pretreated patients, those with high-volume disease and/or poor PS were less likely to benefit from ICI. irAEs were associated with improved OS. TMB correlated with improved survival, but this association was not observed when MSI-high patients were excluded.

Mutational profile of lung carcinoid and gene ontology of mutated genes

PFS analysis by gene alteration occurring in 10% or more of MSS patients who received combination therapy

The Memorial Sloan Kettering Cancer Center (MSK) nomogram combined both gastroesophageal junction (GEJ) and gastric cancer patients and was created in an era from patients who generally did not receive neoadjuvant chemotherapy. We sought to reevaluate the MSK nomogram in the era of multidisciplinary treatment for GEJ and gastric cancer.Using data on patients who underwent R0 resection for GEJ or gastric cancer between 2002 and 2016, the C-index of prediction for disease-specific survival (DSS) was compared between the MSK nomogram and the American Joint Committee on Cancer (AJCC) 8th edition staging system after segregating patients by tumor location (GEJ or gastric cancer) and neoadjuvant treatment. A new nomogram was created for the group for which both systems poorly predicted prognosis.During the study period, 886 patients (645 gastric and 241 GEJ cancer) underwent up-front surgery, and 999 patients (323 gastric and 676 GEJ) received neoadjuvant treatment. Compared with the AJCC staging system, the MSK nomogram demonstrated a comparable C-index in gastric cancer patients undergoing up-front surgery (0.786 vs 0.753) and a better C-index in gastric cancer patients receiving neoadjuvant treatment (0.796 vs 0.698). In GEJ cancer patients receiving neoadjuvant chemotherapy, neither the MSK nomogram nor the AJCC staging system performed well (C-indices 0.647 and 0.646). A new GEJ nomogram was created based on multivariable Cox regression analysis and was validated with a C-index of 0.718.The MSK gastric cancer nomogram's predictive accuracy remains high. We developed a new GEJ nomogram that can effectively predict DSS in patients receiving neoadjuvant treatment.

Purpose: In patients with locally advanced esophageal adenocarcinoma, response to neoadjuvant therapy strongly predicts survival, but robust molecular predictors of response have been lacking. We therefore sought to discover meaningful predictors of response in these patients. Experimental Design: We retrospectively identified all patients with adenocarcinoma of the lower esophagus or gastroesophageal junction who (i) were treated with multimodality therapy with curative intent at our institution from 2014 through 2020 and (ii) underwent prospective sequencing by Memorial Sloan Kettering-Integrated Mutation Profiling of Actionable Cancer Targets. Clinicopathologic and genomic data were analyzed to identify potential genomic features, somatic alterations, and oncogenic pathways associated with treatment response. Results: In total, 237 patients were included. MDM2 amplification was independently associated with poor response to neoadjuvant therapy [OR, 0.10 (95% confidence interval, 0.01–0.55); P = 0.032], when accounting for significant clinicopathologic variables, including clinical stage, tumor grade, and chemotherapy regimen. Moreover, TP53 pathway alterations, grouped according to inferred severity of TP53 dysfunction, were significantly associated with response to neoadjuvant therapy (P = 0.004, q = 0.07). Patients with MDM2 amplifications or truncating biallelic TP53 mutations had similar outcomes in terms of poor responses to neoadjuvant therapy and, consequently, shorter progression-free survival, compared with patients with TP53 pathway wild-type tumors. Thus, worsening TP53 dysfunction was directly correlated with worse outcomes. Conclusions: MDM2 amplification and TP53 status are associated with response to therapy in patients with esophageal adenocarcinoma. Given the dearth of actionable targets in esophageal adenocarcinoma, MDM2 inhibition, in combination with cytotoxic chemotherapy, may represent an important therapeutic strategy to overcome treatment resistance and improve outcomes in these patients.

PURPOSEComprehensive genomic profiling has defined key oncogenic drivers and distinct molecular subtypes in esophagogastric cancer; however, the number of clinically actionable alterations remains limited. To establish preclinical models for testing genomically driven therapeutic strategies, we generated and characterized a large collection of esophagogastric cancer patient–derived xenografts (PDXs).MATERIALS AND METHODSWe established a biobank of 98 esophagogastric cancer PDX models derived from primary tumors and metastases. Clinicopathologic features of each PDX and the corresponding patient sample were annotated, including stage at diagnosis, treatment history, histology, and biomarker profile. To identify oncogenic DNA alterations, we analyzed and compared targeted sequencing performed on PDX and parent tumor pairs. We conducted xenotrials in genomically defined models with oncogenic drivers.RESULTSFrom April 2010 to June 2019, we implanted 276 patient tumors, of which 98 successfully engrafted (35.5%). This collection is enriched for PDXs derived from patients with human epidermal growth factor receptor 2–positive esophagogastric adenocarcinoma (62 models, 63%), the majority of which were refractory to standard therapies including trastuzumab. Factors positively correlating with engraftment included advanced stage, metastatic origin, intestinal-type histology, and human epidermal growth factor receptor 2–positivity. Mutations in TP53 and alterations in receptor tyrosine kinases ( ERBB2 and EGFR), RAS/PI3K pathway genes, cell-cycle mediators ( CDKN2A and CCNE1), and CDH1 were the predominant oncogenic drivers, recapitulating clinical tumor sequencing. We observed antitumor activity with rational combination strategies in models established from treatment-refractory disease.CONCLUSIONThe Memorial Sloan Kettering Cancer Center PDX collection recapitulates the heterogeneity of esophagogastric cancer and is a powerful resource to investigate mechanisms driving tumor progression, identify predictive biomarkers, and develop therapeutic strategies for molecularly defined subsets of esophagogastric cancer.

OBJECTIVE We sought to compare gastroesophageal junction (GEJ) cancer and gastric cancer (GC) and identify clinicopathological and oncological differences. SUMMARY BACKGROUND DATA GEJ cancer and GC are frequently studied together. Although the treatment approach for each often differs, clinicopathological and oncological differences between the 2 have not been fully evaluated. METHODS We retrospectively identified patients with GEJ cancer or GC who underwent R0 resection at our center between January 2000 and December 2016. Clinicopathological characteristics, disease-specific survival (DSS), and site of first recurrence were compared. RESULTS In total, 2194 patients were analyzed: 1060 (48.3%) with GEJ cancer and 1134 (51.7%) with GC. Patients with GEJ cancer were younger (64 vs 66 years; P < 0.001), more often received neoadjuvant treatment (70.9% vs 30.2%; P < 0.001), and had lower pathological T and N status. Five-year DSS was 62.2% in patients with GEJ cancer and 74.6% in patients with GC (P < 0.001). After adjustment for clinicopathological factors, DSS remained worse in patients with GEJ cancer (hazard ratio, 1.78; 95% confidence interval, 1.40-2.26; P < 0.001). The cumulative incidence of recurrence was approximately 10% higher in patients with GEJ cancer (P < 0.001). The site of first recurrence was more likely to be hematogenous in patients with GEJ cancer (60.1% vs 31.4%; P < 0.001) and peritoneal in patients with GC (52.9% vs 12.5%; P < 0.001). CONCLUSIONS GEJ adenocarcinoma is more aggressive, with a higher incidence of recurrence and worse DSS, compared with gastric adenocarcinoma. Distinct differences between GEJ cancer and GC, especially in patterns of recurrence, may affect evaluation of optimal treatment strategies.

Cancer cell plasticity due to the dynamic architecture of interactome networks provides a vexing outlet for therapy evasion. Here, through chemical biology approaches for systems level exploration of protein connectivity changes applied to pancreatic cancer cell lines, patient biospecimens, and cell- and patient-derived xenografts in mice, we demonstrate interactomes can be re-engineered for vulnerability. By manipulating epichaperomes pharmacologically, we control and anticipate how thousands of proteins interact in real-time within tumours. Further, we can essentially force tumours into interactome hyperconnectivity and maximal protein-protein interaction capacity, a state whereby no rebound pathways can be deployed and where alternative signalling is supressed. This approach therefore primes interactomes to enhance vulnerability and improve treatment efficacy, enabling therapeutics with traditionally poor performance to become highly efficacious. These findings provide proof-of-principle for a paradigm to overcome drug resistance through pharmacologic manipulation of proteome-wide protein-protein interaction networks., Joshi, Gomes et al. employ a chemical modulation approach of the cellular interactome to a hyperconnectivity state and show association with the increased response of pancreatic cancer cell lines to specific drugs, including those that target the MAPK-pathways and PI3K-mTOR pathway. To achieve this, the authors employ chemical modulation of the interactome via epichaperome inhibition with the small molecule PU-H71.

This study aimed to analyze timing and sites of recurrence for patients receiving neoadjuvant chemotherapy for gastric cancer. Neoadjuvant chemotherapy followed by surgical resection is the standard treatment for locally advanced gastric cancer in the West, but limited information exists as to timing and patterns of recurrence in this setting. Patients with clinical stage 2 or 3 gastric cancer treated with neoadjuvant chemotherapy followed by curative-intent resection between January 2000 and December 2015 were analyzed for 5-year recurrence-free survival (RFS) as well as timing and site of recurrence. Among 312 identified patients, 121 (38.8%) experienced recurrence during a median follow-up period of 46 months. The overall 5-year RFS rate was 58.9%, with RFS rates of 95.8% for ypT0N0, 81% for ypStage 1, 77.4% for ypStage 2, and 22.9% for ypStage 3. The first site of recurrence was peritoneal for 49.6%, distant (not peritoneal) for 45.5%, and locoregional for 11.6% of the patients. The majority of the recurrences (84.3%) occurred within 2 years. Multivariate analysis showed that ypT4 status was an independent predictor for recurrence within 1 year after surgery (odds ratio, 2.58; 95% confidence interval, 1.10–6.08; p = 0.030). The majority of the recurrences for patients with clinical stage 2 or 3 gastric cancer who received neoadjuvant chemotherapy and underwent curative resection occurred within 2 years. After neoadjuvant chemotherapy, pathologic T stage was a useful risk predictor for early recurrence.

Background Neutrophil-to-lymphocyte ratio (NLR) has been reported as prognostic in pancreatic ductal adenocarcinoma (PDAC). Data about NLR changes during neoadjuvant therapy (NAT) and its relationship with pathological tumor response and survival are lacking. Methods Pancreatic ductal adenocarcinoma patients with NAT followed by resection between 2009 and 2015 were identified from a prospective database. Neutrophil-to-lymphocyte ratio was collected prior to NAT (baseline), on chemotherapy (prior to cycle 3), and prior to surgery. Baseline NLR, and changes in NLR between baseline and on chemotherapy (delta 1) and between baseline and surgery (delta 2) were compared with pathologic response (Results Of 93 patients, 17% had good pathological response. Median (interquartile range) NLR at baseline, third cycle, and surgery were 2.7 (2.0-3.7), 2.5 (1.9-4.1), and 3.1 (2.1-5.3), respectively. Median change in NLR from baseline to third cycle was .06 ( P = .72), and .6 from baseline to surgery ( P < .01). Baseline NLR, delta 1, and delta 2 were not associated with pathological response, OS, or DFS. Discussion Neutrophil-to-lymphocyte ratio increased after NAT, but a significant association between NLR and pathological response, OS, and DFS in resected PDAC patients was not observed.

Objective We sought to determine the extent of lymphadenectomy that optimizes staging and survival in patients with locally advanced esophageal adenocarcinoma (EAC) treated with neoadjuvant chemoradiotherapy followed by esophagectomy. Summary background data Several studies have found that a more extensive lymphadenectomy leads to better disease-specific survival in patients treated with surgery alone. Few studies, however, have investigated whether this association exists for patients treated with neoadjuvant chemoradiotherapy. Methods We examined our prospective database and identified patients with EAC treated with neoadjuvant chemoradiotherapy followed by esophagectomy between 1995 and 2017. Overall survival (OS) and disease-free survival (DFS) were estimated using Kaplan-Meier methods, and a multivariable Cox proportional hazards model was used to identify independent predictors of OS and DFS. The relationship between the total number of nodes removed and 5-year OS or DFS was plotted using restricted cubic spline functions. Results In total, 778 patients met the inclusion criteria. The median number of excised nodes was 21 (interquartile range, 16-27). A lower number of excised lymph nodes was independently associated with worse OS and DFS (OS: hazard ratio [HR], 0.98; confidence interval [CI], 0.97-1.00; P = 0.013; DFS: HR, 0.99; CI, 0.98-1.00; P = 0.028). Removing 25 to 30 lymph nodes was associated with a 10% risk of missing a positive lymph node. Both OS and DFS improved with up to 20 to 25 lymph nodes removed, regardless of treatment response. Conclusions The optimal extent of lymphadenectomy to enhance both staging and survival following chemoradiotherapy, regardless of treatment response, is approximately 25 lymph nodes.

Genetic alterations of tumor suppressor genes (TSGs) are frequently observed to have cumulative or cooperative tumorigenic effects. We examined whether the TSGs Rb1, Trp53, Pten and Men1 have cooperative effects in suppressing neuroendocrine tumors (NETs) in mice. We generated pairwise homozygous deletions of these four genes in insulin II gene expressing cells using the Cre-LoxP system. By monitoring growth and examining the histopathology of the pituitary (Pit) and pancreas (Pan) in these mice, we demonstrated that pRB had the strongest cooperative function with PTEN in suppressing PitNETs and had strong cooperative function with Menin and TRP53, respectively, in suppressing PitNETs and PanNETs. TRP53 had weak cooperative function with PTEN in suppressing pituitary lesions. We also found that deletion of Pten singly led to prolactinomas in female mice, and deletion of Rb1 alone led to islet hyperplasia in pancreas. Collectively, our data indicated that pRB and PTEN pathways play significant roles in suppressing PitNETs, while the Menin-mediated pathway plays a significant role in suppressing PanNETs. Understanding the molecular mechanisms of these genes and pathways on NETs will help us understand the molecular mechanisms of neuroendocrine tumorigenesis and develop effective preclinical murine models for NET therapeutics to improve clinical outcomes in humans.

By the strictest of definitions, a genetic driver of tumorigenesis should fulfill two criteria: it should be altered in a high percentage of patient tumors, and it should also be able to cause the same type of tumor to form in mice. No gene that fits either of these criteria has ever been found for ileal neuroendocrine tumors (I-NETs), which in humans are known for an unusual lack of recurrently mutated genes, and which have never been detected in mice. In the following report, we show that I-NETs can be generated by transgenic RT2 mice, which is a classic model for a genetically unrelated disease, pancreatic neuroendocrine tumors (PNETs). The ability of RT2 mice to generate I-NETs depended upon genetic background. I-NETs appeared in a B6AF1 genetic background, but not in a B6 background nor even in an AB6F1 background. AB6F1 and B6AF1 have identical nuclear DNA but can potentially express different allelic forms of imprinted genes. This led us to test human I-NETs for loss of imprinting, and we discovered that the IGF2 gene showed loss of imprinting and increased expression in the I-NETs of 57% of patients. By increasing IGF2 activity genetically, I-NETs could be produced by RT2 mice in a B6 genetic background, which otherwise never developed I-NETs. The facts that IGF2 is altered in a high percentage of patients with I-NETs and that I-NETs can form in mice that have elevated IGF2 activity, define IGF2 as the first genetic driver of ileal neuroendocrine tumorigenesis.

458 Background: Microbial dysbiosis has been shown to be associated with the pathogenesis of gastric cancer (GC). However, the relationship between the GC microbiome and response to systemic therapy, such as neoadjuvant chemotherapy (NAC), is largely unknown. This study aims to explore changes in the microbiome after neoadjuvant chemotherapy, by analyzing the microbial profile of patients who received NAC and comparing differences among those with varied pathologic response to therapy. Methods: A microbiome bioinformatics pipeline using multiple next generation sequencing platforms was developed and used for analysis. GC tissue from patients who received NAC (n=101) and those who did not (n=85) were acquired at the time of surgical resection. Shannon alpha diversity plot and enrichment analyses by odds ratio were used to compare the microbial differences of the treatment cohorts. The microbial profiles of patients with pathologic response to NAC (>20% response) were characterized. Results: Of patients who received NAC, 66 (65.3%) experienced a greater than 20% response to NAC, and 35 (34.6%) demonstrated a 20% or lower response. Patients with a pathologic response to NAC were enriched for Rhizobium, Streptomyces, Comamonas, Sphingomonas, Micrococcus, Mycobacterium, Thauera, Hyphomicrobium, and Sinorhizobium (OR>4). There were no statistically significant differences in alpha diversity (p>0.05). Conclusions: Our results demonstrate that patients with a greater than 20% pathologic response to NAC have a distinct microbial enrichment compared to those with a poor pathologic response. Given the variable NAC treatment responses in GC, understanding unique microbial signatures in tumors will provide the landscape to explore key microbial contributors to GC NAC treatment response that may improve our understanding of treatment response variability among patients. [Table: see text]

299 Background: Although epidemiological and clinical differences in gastric cancer (GC) between the US and Japan have been reported, genetic differences have not been clarified. We aimed to characterize molecular differences in GC between the two countries. Methods: We collected data between January 2010 and December 2019 from a prospectively maintained database of GC at our US and Japanese centers. After matching clinicopathological backgrounds, including age, sex, clinical T and N status, and tumor location, the genomic profiles of the primary site were compared for 58 patients in each group undergoing surgical resection and had MSK-IMPACT (MSK-Integrated Mutation Profiling of Actionable Cancer Targets), a tumor-normal next generation sequencing assay that can detect alterations in exons and select introns of 505 genes. The MSI sensor algorithm was used to assess microsatellite instability. Genomic alterations were filtered for driver variants using OncoKB, and genes were consolidated into pathways using curated pathway templates from the Cancer Genome Atlas. Results: The clinicopathological characteristics were well matched between 58 patients in each cohort. In the entire cohort, the most commonly altered genes were: TP53 (45%), ARID1A (24%), and ERBB2 (17%) in the US cohort, and TP53 (50%), ARID1A (19%), and ERBB2 (17%) in the Japanese cohort. Although KMT2D was more frequently altered in the US cohort (19% vs. 2%), the two cohorts had no significant differences in other altered genes and gene pathways. The tumor with MSI high was found more frequently in the US cohort (22.4% vs. 5.2%, p = 0.01). Among the MSI-normal tumors, the tumor mutational burden (US: 3.5 muts/Mb and Japanese: 4.1 muts/Mb) and the fraction genome altered (US: 0.37 and Japanese: 0.28) did not significantly differ between the two groups. Additionally, no genes or pathways were significantly enriched in either group. Patterns of mutual exclusivity and co-occurrence amongst genes and pathways were also similar between the two groups. Conclusions: In this original genomic comparison of US and Japanese gastric cancers, matching clinicopathological backgrounds, Japanese and US gastric cancers are remarkably similar at the genomic level, with the possible exception of MSI-high tumor that appear to be more frequent in the US.

Nerves are a component of the tumor microenvironment contributing to cancer progression, but the role of cells from nerves in facilitating cancer invasion remains poorly understood. Here we show that Schwann cells (SC) activated by cancer cells collectively function as tumor-activated Schwann cell tracks (TAST) that promote cancer cell migration and invasion. Nonmyelinating SCs form TASTs and have cell gene expression signatures that correlate with diminished survival in patients with pancreatic ductal adenocarcinoma. In TASTs, dynamic SCs form tracks that serve as cancer pathways and apply forces on cancer cells to enhance cancer motility. These SCs are activated by c-Jun, analogous to their reprogramming during nerve repair. This study reveals a mechanism of cancer cell invasion that co-opts a wound repair process and exploits the ability of SCs to collectively organize into tracks. These findings establish a novel paradigm of how cancer cells spread and reveal therapeutic opportunities. Significance: How the tumor microenvironment participates in pancreatic cancer progression is not fully understood. Here, we show that SCs are activated by cancer cells and collectively organize into tracks that dynamically enable cancer invasion in a c-Jun–dependent manner. See related commentary by Amit and Maitra, p. 2240. This article is highlighted in the In This Issue feature, p. 2221

Purpose The ability of the T‐cell–inflamed gene expression profile (GEP) to predict clinical outcome in esophageal cancer (EC) is unknown. This retrospective observational study assessed the prognostic value of GEP and programmed death ligand 1 (PD‐L1) expression in patients with EC treated in routine clinical practice. Methods Tumor samples of 294 patients from three centers in Denmark, South Korea, and the United States, collected between 2005 and 2017, were included. T‐cell–inflamed GEP score was defined as non‐low or low using a cutoff of −1.54. A combined positive score (CPS) ≥10 was defined as PD‐L1 expression positivity. Associations between overall survival (OS) and GEP status and PD‐L1 expression were explored by Cox proportional hazards models adjusting for age, sex, histology, stage, and performance status. Results Median age was 65 years; 63% of patients had adenocarcinoma (AC) and 37% had squamous cell carcinoma (SCC). Thirty‐six percent of tumors were GEP non‐low, with higher prevalence in AC (46%) than SCC (18%). Twenty‐one percent were PD‐L1–positive: 32% in South Korean samples versus 16% in non‐Asian samples and 26% in SCC versus 18% in AC. GEP scores and PD‐L1 CPS were weakly correlated (Spearman’s R = 0.363). OS was not significantly associated with GEP status (non‐low vs low; adjusted hazard ratio, 0.91 [95% CI, 0.69–1.19]) or PD‐L1 expression status. Conclusion Neither GEP nor PD‐L1 expression was a prognostic marker in Asian and non‐Asian patients with EC., In a cohort of 294 patients with esophageal adenocarcinoma and esophageal squamous cell carcinoma from Denmark, South Korea, and the United States, T‐cell–inflamed gene expression profile (GEP) score (non‐low vs low) and PD‐L1 expression status (CPS ≥10 vs CPS