Preoperative chemoradiation therapy induces primary-tumor complete response more frequently than chemotherapy alone in gastric cancer: analyses of the National Cancer Database 2006-2014 using propensity score matching.

Background: The benefit of preoperative chemoradiation (CXRT) over preoperative chemotherapy alone ("chemotherapy" hereafter) is unknown. By analyzing the National Cancer Database (NCDB), we investigated whether preoperative CXRT improves the incidence of primary tumor pathologic complete response (ypT0) and overall survival (OS) compared with preoperative chemotherapy in patients with gastric cancer.

Methods: Patients with non-metastatic gastric adenocarcinoma who underwent CXRT or chemotherapy followed by gastrectomy were included. Propensity score matching with a ratio of 1:1 was implemented to reduce selection bias. A conditional logistic regression model was used to compare incidences of ypT0 between groups, and Cox proportional hazards model was used to compare OS.

Results: We identified 8464 patients. Median patient age was 63 years; 76% were male and 79% were white. ypT0 was observed in 16.1% of patients in the CXRT group and 6.6% in the chemotherapy group (p < 0.001). After propensity score matching, a total of 2408 patients were matched. CXRT was associated with a higher incidence of ypT0 (OR 2.28, 95% CI 1.76-2.95; p < 0.0001) and higher frequency of R0 resection (92 vs. 86%; p < 0.001). However, CXRT was not associated with longer OS (HR 1.03, 95% CI 0.92-1.15; p = 0.63). Safety profiles (30-day mortality, 30-day readmission, and length of hospital stay) were equivalent between groups.

Conclusions: In this study of gastric cancer patients from the NCDB, CXRT was associated with a higher incidence of ypT0 and R0 resection compared with chemotherapy, although it was not associated with a longer OS.