Effect of preoperative radiotherapy on survival of advanced gastric signet-ring cell carcinoma

Abstract

Neoadjuvant chemotherapy could reduce the clinical stage of advanced gastric cancer (AGC) and lead to survival benefits for patients. Nevertheless, the clinical value of preoperative radiotherapy in AGC, especially in signet ring cell carcinoma (SRCC) patients, remains unclear. In this study, AGC patients (stages II-IV) registered in the Surveillance, Epidemiology, and End Results (SEER) Program receiving surgery between 1988 and 2013 were analyzed. The histopathological types were confirmed as SRCC, mucinous adenocarcinoma (MC), and adenocarcinoma (AC). A total of 15,015 AGC patients were included in our cohort, with most patients diagnosed with AC (n = 9,698, 64.59%). SRCC and MC were found in 4,570 (30.44%) and 747 (4.98%) patients, respectively. The chi-square test was selected to compare the correlations of clinicopathological parameters between the three groups. The risk factors for survival were assessed using univariate and multivariate Cox proportional hazards models. The clinical characteristics of SRCC patients differed significantly from those of AC and MC patients. Compared with MC and AC, SRCC was more unfavorable for the survival of patients with AGC (SRCC vs. MC vs. AC: Ref.; HR: 0.872, 95% CI: 0.796-0.955, P = 0.003; HR: 0.920, 95% CI: 0.881-0.961, P < 0.001). However, preoperative radiotherapy was not an independent prognostic factor in AGC (HR: 1.050, 95% CI: 0.972-1.135, P = 0.215). Whether in patients with AGC, stage III, or stage IV gastric cancer, preoperative radiotherapy did not affect the survival of SRCC patients, with no difference in the 5-year survival rate. In particular, in stage II SRCC patients, the 5-year survival rate of the surgery-alone group was higher than that of the preoperative radiotherapy group (50.7% vs. 34.0%, P = 0.004). Therefore, preoperative radiotherapy could not provide any significant survival benefit for advanced gastric SRCC patients and even led to a worse prognostic outcome among stage II SRCC patients.