56 Background: The biopsy specimen by endoscopy can only show the surface of its gene profiles. We hypothesis whether the biopsy specimen can reflect all part of gene profile or not. We tested how 5-FU related genes and angiogenesis gene expressed in the invasion depth in the primary tumor of the Stage II or III advanced gastric cancer. Methods: Twenty-five patients with stage II or III advanced gastric cancer who underwent gastrectomy were analyzed.Formalin-fixed, paraffin-embedded tumor tissues were dissected from the surface section (mainly mucosa), the middle section (mainly submucossa) and the deep section (the part invaded most deeply) of the primary tumor and the normal gastric mucosa tissue by the laser-captured microdissection technique and were analyzed for target gene expressions using a quantitative real-time polymerase chain reaction.We analyzed for target genes as TS, TP, DPD, ERCC1, EGFR, VEGF and HIF1α. Results: In the primary tumor, TP and HIF1α gene expression in the surface section was significantly higher than in the deep section (p=0.021, p=0.012). These gene expression and the depth of the primary tumor had a correlation coefficient (TP; r=0.29, HIF1α; r=0.33). There was no significantly difference between surface and deep section in the primary tumor in TS, DPD, ERCC1, VEGF, EGFR except TP and HIF1α. There was no significantly difference between surface and middle section in the primary tumor in all gene expression. There was no significantly difference between middle and deep section in the primary tumor in all gene expression. Conclusions: Only TP and HIF1α had tendency that these gene expression became higher as invaded from the surface section to the deep section of primary tumor. These data suggested that biopsy specimens could be predicted gene expression profile from the surface of gastric cancer. But as you know, gastric cancer has a heterogeneity gene profile. We need at least few samples to say whole gene expression of its tumors. This is preliminary data, it will need further study to proof these result.
LBA-04 Clinical outcomes and their correlation with gene expression in patients with advanced gastric cancer treated with pembrolizumab (MK-3475): KEYNOTE-012
