HER2 status and histopathologic findings related to tumor regression in gastric carcinomas treated with preoperative chemotherapy.

145 Background: Neoadjuvant chemotherapy is now the standard of care of patients with resectable gastric carcinomas (GC). Predictive molecular markers and histopathological evidence of tumour response to chemotherapy are not widely available. In this study we evaluated HER2 status and histopathological features associated with tumor regression in 36 GC treated with neoadjuvant chemotherapy followed by surgery. Methods: 36 patients had received ECF, DCF or ECX chemotherapy prior the surgery. The entire tumor beds of the specimens were histologically evaluated. HER2 expression by immunohistochemistry was detected in the biopsy and gastrectomy specimens. Results: 46% of the cases were intestinal type, 40% were diffuse and 14% were unclassified. Nine patients had major clinical and radiological response (CRR) characterized by presence of viable tumor cells less than 50% of the tumor with increased fibrosis (>50%). Three cases had complete CRR showing tumor beds totally replaced by fibrosis. The remaining case...