BACKGROUND: No studies have investigated whether race/ethnicity is associated with the recommended use of preoperative chemotherapy or subsequent outcomes in gastric cancer. To determine whether there is such an association, analyses of patients with gastric cancer in the National Cancer Data Base (NCDB) were performed.METHODS: Patients with clinical T2‐4bN0‐1M0 gastric adenocarcinoma, as defined by the eighth edition of the American Joint Committee on Cancer staging manual, who underwent gastrectomy from 2006 to 2014 were identified from the NCDB. Multiple logistic regression was conducted to examine factors associated with preoperative chemotherapy use.RESULTS: This study identified 16,945 patients who met the criteria, and 8286 of these patients (49%) underwent preoperative chemotherapy. The use of preoperative chemotherapy remarkably increased over the study period, from 34% in 2006 to 65% in 2014. Preoperative chemotherapy was more commonly used for cardia tumors than noncardia tumors (83% vs 44% in 2014). In a multivariable analysis, races and ethnicities other than non‐Hispanic (NH) white race were associated with less frequent use of preoperative chemotherapy in comparison with NH whites after adjustments for social, tumor, and hospital factors. The insurance status and the education level mediated an enhanced effect of racial/ethnic disparities in preoperative chemotherapy use. The use of preoperative chemotherapy and radiation therapy was associated with reduced racial/ethnic disparities in overall survival.CONCLUSIONS: Racial/ethnic disparities in the use of preoperative chemotherapy and in outcomes exist among patients with gastric cancer in the United States. Efforts to improve the access to high‐quality cancer care in minority groups may reduce racial disparities in gastric cancer in the United States. Cancer 2018;124:998‐1007. © 2018 American Cancer Society.

BACKGROUND. Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies, with unpredictable responses to chemotherapy. Approaches to assay patient tumors before treatment and identify effective treatment regimens based on tumor sensitivities are lacking. We developed an organoid-based platform (OBP) to visually quantify patient-derived organoid (PDO) responses to drug treatments and associated tumor-stroma modulation for personalized PDAC therapy. METHODS. We retrospectively quantified apoptotic responses and tumor-stroma cell proportions in PDOs via 3D immunofluorescence imaging through annexin A5, α-smooth muscle actin (α-SMA), and cytokeratin 19 (CK-19) levels. Simultaneously, an ex vivo organoid drug sensitivity assay (ODSA) was used to measure responses to standard-of-care regimens. Differences between ODSA results and patient tumor responses were assessed by exact McNemar’s test. RESULTS. Immunofluorescence signals, organoid growth curves, and Ki-67 levels were measured and authenticated through the OBP for up to 14 days. ODSA drug responses were not different from patient tumor responses, as reflected by CA19-9 reductions following neoadjuvant chemotherapy (P = 0.99). PDOs demonstrated unique apoptotic and tumor-stroma modulation profiles (P < 0.0001). α-SMA/CK-19 ratio levels of more than 1.0 were associated with improved outcomes (P = 0.0179) and longer parental patient survival by Kaplan-Meier analysis (P = 0.0046). CONCLUSION. Heterogenous apoptotic drug responses and tumor-stroma modulation are present in PDOs after standard-of-care chemotherapy. Ratios of α-SMA and CK-19 levels in PDOs are associated with patient survival, and the OBP could aid in the selection of personalized therapies to improve the efficacy of systemic therapy in patients with PDAC. FUNDING. NIH/National Cancer Institute grants (K08CA218690, P01 CA117969, R50 CA243707-01A1, U54CA224065), the Skip Viragh Foundation, the Bettie Willerson Driver Cancer Research Fund, and a Cancer Center Support Grant for the Flow Cytometry and Cellular Imaging Core Facility (P30CA16672).