Association of histologic grade and subtypes of gastric cancer (GC) with chemoradiation response.

97 Background: Patients with localized gastric cancer (LGC), when treated with preoperative therapy, tend to have heterogeneous and unpredictable outcomes. Currently, no clinical variables or biomarkers can predict response. Methods: We analyzed 107 LGC patients who were treated with chemoradiation followed by surgery (trimodality therapy; TMT). Tumors were grouped into poorly (G3) or moderately (G2) differentiated and signet ring cell (SRC) or non-SRC histology. Association was made with pathologic complete response (pathCR) or < pathCR. Descriptive statistics and survival analyses were utilized. Results: The majority of the patients were male (60%), had clinical stage III cancer (51%), and received chemotherapy before chemoradiation (94%). All had adenocarcinoma and most had G3 (78%) and SRC histology (58%). PathCR was noted in 18% of patients with G3 and 33% of patients with G2 (p=0.125). Overall survival (OS) was significantly shorter for G3 patients compared to G2 patients (p=0.045). Patients with SR...