The effects of combined modality therapy on stage II-III primary gastric signet ring cell carcinoma.

Abstract

e16530 Background: To date, there is no well-defined standard of care for gastric signet ring cell carcinoma (GSRC). Clinical guidelines support that combined modality therapy (CMT) on localized gastric cancer, but this may not be appropriate for GSRC as it was generally found to be chemo-resistant. We conducted a population-based study to examine the effects of therapeutic strategies on survival outcomes by using the Surveillance, Epidemiology, and End Results (SEER) data. Methods: Analyses included primary GSRC patients with stage II-III who survived more than 6 months, and were diagnosed between 2006 and 2016 from SEER data.CMT were categorized as gastrectomy group, adjuvant CT group (gastrectomy with adjuvant chemotherapy), neoadjuvant RT group (gastrectomy with neoadjuvant radiotherapy combined adjuvant chemotherapy), and adjuvant CRT group (gastrectomy with chemoradiotherapy). Survival analyses were conducted by Kaplan-Meier method and multivariate Cox proportional hazards models, adjusted for age, gender, race, marital status, histology, AJCC stage, tumor location, and lymph nodes removed. Models were stratified by gender, AJCC stage, lymph nodes removed and tumor location. Results: Of the 1,717 cases of stage II-III primary GSRC, the mean age was 66.9 (SD: 11.0) years, over a half were male (52.8%), and the majority were white (66.0%). A total of 39.9% received adjuvant CRT. The five-year overall survival (OS) rate was 34.6% for this treatment, and 29.6% for adjuvant CT group, 25.4% for adjuvant CRT group, only 23.8% for the gastrectomy group. The median OS of patients treated with adjuvant CRT was significantly longer than that of the gastrectomy group (33 vs 24 months, aHR = 0.71, 95%CI = 0.60,0.84). Although the crude model showed a significant association between adjuvant CT and total survival (cHR = 0.81, 95%CI = 0.68,0.96), the effect measure turned null in the multivariable and sub-group analysis. Independent prognostic factors were adjuvant CRT, ≥60 years old, AJCC stage, and > 20 lymoh nodes removed. Conclusions: In this study, GSRC patients with stage II-III experienced improved overall survival after receiving adjuvant CRT, which provides several treatment implications. Future clinical trials considering adjuvant CRT will be needed to verify the conclusion derived from this study.