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

Abstract

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 cases had minimal CRR characterized by viable tumor cells in more than 50% and minimal fibrosis. Necrosis was not found; mucinous metaplasia was observed in three cases of the major CRR. Inflammatory infiltrated was found in all cases. The downstaging of T-stage seems to be greater in the intestinal type than diffuse type (80% vs 44%). HER2+ (score 3) was detected in 16,6% of the biopsy specimen. Only 1 case was HER2+ in the biopsy and in the gastrectomy tissue. All the HER2+ GC showed minimal CRR. Conclusions: The ratio of viable tumor cells and fibrosis is directly associated with tumor response to preoperative chemotherapy. The chemotherapy regimens seem to collaborate to downstaging rates; however the treatment of HER2+ GC group could be improved by the use of Ttrastuzumab.