Adjuvant Radiochemotherapy versus Chemotherapy Alone for Gastric Cancer: Implications for Target Definition.

The INT0116 trial was a milestone study and laid the foundation for the adjuvant radiotherapy (RT) associated to concurrent chemotherapy (CT) for the treatment of gastric cancer (GC) after gastrectomy. However, it is still controversial whether adding RT to CT could further benefit D2-dissected GC patients. The ARTIST trial indicated that the addition of RT to CT did not have a positive impact on disease-free survival (DFS). Nevertheless, in a subgroup of 396 patients with positive pathological lymph nodes, combined treatment with RT was superior to CT alone. A similar randomized Chinese trial confirmed the superiority of adding RT to CT in terms of DFS for patients with D2 lymphadenectomy. However, several previous randomized studies provided inconsistent results with the benefits of combined treatment of RT and CT. The inconsistent results of several studies may be due to the differences between tumor epidemiology, treatment policies, and treatment outcomes. During the past decade, major progress in accurate target delineation utilizing RT technology has been observed. However, even though the use of adjuvant RT doubled after the INT-0116 trial results became public, the fraction of patients receiving adjuvant RT was still low according to the SEER database. The low rate of adjuvant RT can partially be explained by concern over toxicity while undergoing RT. Several studies have also defined the specific location of locoregional recurrence for postoperative RT in GC, but these studies are still limited. A number of retrospective studies demonstrated that the most prevalent nodal recurrence was outside the D2 dissection field. In order to overcome the restricted nature of a retrospective study and provide more individual radiation field determination, additional large-scale prospective multicenter studies are required to evaluate the optimal RT target.