Chemotherapy is ubiquitous in first-line treatment of advanced gastric cancer, yet responses are heterogeneous, and little is known about mediators of chemotherapy response. To move forward, an understanding of the effects of standard chemotherapy on the tumor–immune microenvironment (TME) is needed. Coupling whole-exome sequencing, bulk RNA and single-cell transcriptomics from paired pretreatment and on-treatment samples in treatment-naïve patients with HER2-positive and HER2-negative gastric cancer, we define features associated with response to platinum-based chemotherapy. Response was associated with on-treatment TME remodeling including natural killer (NK) cell recruitment, decreased tumor-associated macrophages, M1-macrophage repolarization, and increased effector T-cell infiltration. Among chemotherapy nonresponders, we observed low/absent PD-L1 expression or modulation, on-treatment increases in Wnt signaling, B-cell infiltration, and LAG3-expressing T cells coupled to an exodus of dendritic cells. We did not observe significant genomic changes in early on-treatment sampling. We provide a map of on-treatment TME modulation with standard chemotherapy and nominate candidate future approaches. Significance: Using paired pretreatment and on-treatment samples during standard first-line chemotherapy, we identify chemotherapy-induced NK-cell infiltration, macrophage repolarization, and increased antigen presentation among responders. Increased LAG3 expression and decreased dendritic cell abundance were seen in nonresponders, emphasizing remodeling of the TME during chemotherapy response and resistance. This article is highlighted in the In This Issue feature, p. 873

Few studies have compared the long-term outcomes of endoscopic resection and surgery. The aim of this study was to compare the long-term outcomes of endoscopic resection with those of surgery for early gastric cancer (EGC). We reviewed prospectively collected data of patients who had undergone endoscopic resection (1,290 patients) or surgery (1,273 patients) for EGC. To reduce the effect of selection bias, we performed a propensity score-matching analysis between the two groups. The primary outcome was overall survival (OS). The secondary outcomes were disease-specific survival, disease-free survival (DFS), recurrence-free survival (RFS), occurrence of metachronous gastric cancer, treatment-related complications, length of hospital stay, and 30-day outcomes. The study was designed as a non-inferiority study and tested in an intention-to-treat analysis. In a propensity-matched analysis of 611 pairs, the 10-year OS proportion was 96.7% in the endoscopic resection group and 94.9% in the surgery group (P=0.120) (risk difference −1.8%, 95% confidence interval (CI) −4.04–0.44, P_{non-inferiority}=0.014), which met the non-inferiority criterion. In contrast, the 10-year RFS proportion was 93.5% in the endoscopic resection group and 98.2% in the surgery group (P<0.001) (risk difference 4.7%, 95% CI 2.50–6.97, P_{non-inferiority}=0.820), which did not meet the non-inferiority criterion, mainly because of metachronous recurrence in the endoscopic resection group. The rate of early complications was higher in the endoscopic resection group than in the surgery group (9.0 vs. 6.6%, P=0.024), whereas the rate of late complications was higher in the surgery group than in the endoscopic resection group (0.5 vs. 2.9%, P<0.001). In the multiple Cox regression analysis, patient’s age, the comorbidity index, the performance index, sex, tumor morphology, and depth of invasion were predictors of OS in patients with EGC. Endoscopic resection might not be inferior to surgery with respect to OS in patients with EGC lesions that meet the absolute or expanded criteria. However, DFS, RFS, and metachronous RFS might be lower after endoscopic resection than after surgery.

Although surgery was the standard treatment for early gastrointestinal cancers, endoscopic resection is now a standard treatment for early gastrointestinal cancers without regional lymph node metastasis. High-definition white light endoscopy, chromoendoscopy, and image-enhanced endoscopy such as narrow band imaging are performed to assess the edge and depth of early gastrointestinal cancers for delineation of resection boundaries and prediction of the possibility of lymph node metastasis before the decision of endoscopic resection. Endoscopic mucosal resection and/or endoscopic submucosal dissection can be performed to remove early gastrointestinal cancers completely by en bloc fashion. Histopathological evaluation should be carefully made to investigate the presence of risk factors for lymph node metastasis such as depth of cancer invasion and lymphovascular invasion. Additional treatment such as radical surgery with regional lymphadenectomy should be considered if the endoscopically resected specimen shows risk factors for lymph node metastasis. This is the first Korean clinical practice guideline for endoscopic resection of early gastrointestinal cancer. This guideline was developed by using mainly de novo methods and encompasses endoscopic management of superficial esophageal squamous cell carcinoma, early gastric cancer, and early colorectal cancer. This guideline will be revised as new data on early gastrointestinal cancer are collected.

Lee H, et al. J Neurogastroenterol Motil. 2013 Apr;19(2):244-250. http://dx.doi.org/10.5056/jnm.2013.19.2.244