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 SRC histology had a lower rate of pathCR than those with non-SRC (8% vs 40%, p<0.001). Patients with SRC histology had a trend towards shorter OS (p=0.063). Surgical pathologic stage was independently associated with OS and recurrence-free survival (RFS) (p<0.001). Conclusions: Our data suggest that histologic grade/ subtypes are associated with response to preoperative chemoradiation. Independent validation and addition of biomarkers could allow individualization of therapy of LGC patients. From U. T. M. D. Anderson Cancer Center (UTMDACC), Houston, Texas, USA. (Supported in part by UTMDACC, and CA 138671 and CA172741 from the NCI). Dr. Nikolaos Charalampakis has been awarded a scholarship from the Hellenic Society of Medical Oncology.