Based on research conclusions from previous studies, the prognosis of GSRCC remains controversial [8-10]. In early GC, the prognosis of GSRCC is better than that of non-GSRCC; however, in advanced stages, the prognosis of GSRCC is worse than that of non-GSRCC. Several reports have shown that a high risk of lymph node metastasis and early peritoneal dissemination could be associated with a worse prognosis [9, 11], due to CDH1-gene mutations and E-cadherin deficiency . Some studies suggest that GSRCC is insensitive to chemotherapy, neither postoperative nor preoperative chemotherapy improves prognosis [2, 9, 11, 13, 14]. Several trials such as ARTIST  and INT0116  have proven that radiotherapy can improve the prognosis of gastric adenocarcinoma.
However, trials targeting the efficacy of radiotherapy in GSRCC patients are scanty and the specific regimens for GSRCC remain uncertain. A previous study using the same database to extract eligible patients but only compare those with and without preoperative radiotherapy has shown that preoperative radiotherapy is associated with significant survival benefits for the patients with advanced GSRCC . In the present study, we divided the study population and the outcomes into three different groups (surgery alone, surgery+pre-operative radiotherapy and surgery+post-operative radiotherapy) thus giving a broader look on the topic. We found that compared with surgery alone, postoperative radiotherapy may improve the prognosis of GSRCC patients, which is consistent with another previous study based on the SEER database . However, these conclusions remain disputed. Zhu et al  reported that adjuvant chemoradiotherapy was associated with poor survival compared with adjuvant chemotherapy in GSRCC patients with D2 gastrectomy, with a median follow-up of 80.5 months and the 3-year OS rate was significantly higher in the chemotherapy group (70.5% vs. 58.6, HR = 0.633, p = 0.017). Hence, further research should be undertaken to clarify this discrepancy.
Contrary to expectations, we found that preoperative radiotherapy did not improve the CSS compared to surgery alone and that postoperative radiotherapy showed a slightly better prognosis than preoperative radiotherapy. This could be owing to the fact that adjacent organs such as the liver and duodenum can reduce the dosage of radiation on lymph node drainage regions. Another possible explanation is that there is still no comprehensive understanding of lymph node drainage region in GSRCC and target regions of GSRCC have not achieved consensus, which may lead to the inaccuracy of radiotherapy. Currently, most studies do not offer compelling evidence on this issue; therefore, more randomized controlled trials are required in further studies.
Furthermore, using univariate and multivariate analyses, we found that the TNM stage was an independent prognostic factor and depth of infiltration was excluded by multivariate analysis. This result suggested that compared with the T stage, lymph node metastasis was considered to be a significant prognostic factor, which was consistent with conclusions from previous related researches [19, 20]. Besides, tumor size is another important factor affecting prognosis and lymph node metastasis. Jun et al  suggested that tumor size over 3.5 cm was an independent risk factor for GC patients. An et al  observed 1043 cases of submucosa infiltration in early GC and found that a tumor diameter over 2 cm was an independent risk factor for lymph node metastasis. Consistent with these researches, we found that tumor size was also an important prognostic factor in patients with GSRCC.