Multimodal Therapy Versus Primary Surgery for Gastric and Gastroesophageal Junction Diffuse Type Carcinoma, with a Focus on Signet Ring Cell Carcinoma: A Nationwide Study

Background: Diffuse type adenocarcinoma and, more specifically, signet ring cell carcinoma (SRCC) of the stomach and gastroesophageal junction (GEJ) have a poor prognosis and the value of neoadjuvant chemo(radio)therapy (nCRT) is unclear.Methods: All patients who underwent surgery for diffuse type gastric and GEJ carcinoma between 2004 and 2015 were retrospectively included from the Netherlands Cancer Registry. The primary outcome was overall survival after surgery. Kaplan-Meier curves were plotted. Furthermore, multivariable Poisson and Cox regressions were performed, correcting for confounders. To comply with the Cox regression proportional hazard assumption, gastric cancer survival was split into two groups, i.e. <90 days and >90 days, postoperatively by adding an interaction variable.Results: Analyses included 2046 patients with diffuse type cancer: 1728 gastric cancers (50% SRCC) and 318 GEJ cancers (39% SRCC). In the gastric cancer group, 49% received neoadjuvant chemotherapy (nCT) and 51% received primary surgery (PS). All-cause mortality within 90 days postoperatively was lower after nCT (hazard ratio [HR] 0.29, 95% confidence interval [CI] 0.20-0.44; p < 0.001). Also after 90 days, mortality was lower in the nCT group (HR for the interaction variable 2.84, 95% CI 1.87-4.30, p < 0.001; total HR 0.29*2.84 = 0.84). In the GEJ group, 38% received nCT, 22% received nCRT, and 39% received PS. All-cause mortality was lower after nCT (HR 0.63, 95% CI 0.43-0.93; p = 0.020) compared with PS. The nCRT group was removed from the Cox regression analysis since the Kaplan-Meier curves of nCRT and PS intersected. The results for gastric and GEJ carcinomas were similar between the SRCC and non-SRCC subgroups.Conclusion: For gastric and GEJ diffuse type cancer, including SRCC, nCT was associated with increased survival.