Prognostic Value of Nodal Response After Preoperative Treatment of Gastric Adenocarcinoma

Background: Pathologically positive lymph nodes (ypN+) after preoperative chemotherapy are associated with poor survival in patients with gastric cancer. Little is known about the association between response to preoperative therapy and the benefit of postoperative therapy. Methods: This retrospective cohort study of the National Cancer Database included patients with clinically node-positive (cN+) gastric cancer treated with preoperative therapy followed by surgery (2006-2014). Preoperative treatment modality was categorized as the inclusion of radiation therapy (RT) or chemotherapy alone. Pretreatment clinical and pathologic stages were used to determine pathologic treatment response rates. The association between overall risk of death and preoperative treatment, disease response, and adjuvant therapy use was evaluated using multivariable Cox regression. Results: Preoperative RT was used in 53.6% of 1,976 patients with cN+ gastric cancer, (74.3% cardia and 10.1% noncardia). The nodal response rate was 38.9% and was higher with RT than with chemotherapy alone (cardia, 46.0% vs 29.1%; P<.001; noncardia, 43.8% vs 31.9%; P=.06). Preoperative RT was associated with an approximate 2-fold increase in the odds of pathologic response compared with chemotherapy. Overall, use of adjuvant therapy was not associated with a decreased risk of death. A primary tumor response with residual nodal disease was not associated with survival (hazard ratio [HR], 1.03; 95% CI, 0.66-1.60). However, a nodal response with residual primary disease was significantly associated with survival (HR, 0.54; 95% CI, 0.44-0.65). Conclusions: More than one-third of node-positive gastric cancers showed pathologic nodal response with preoperative treatment. RT is associated with a higher response than chemotherapy. Patients with ypN+ disease have worse survival, regardless of whether they receive postoperative therapy. Future gastric cancer trials should evaluate the role of preoperative RT and individualize postoperative therapy use.