MO1-18-2Analysis of metastatic foci using in house Gastric 58 SMG panel of 351,050 nt and d/pMMR status by IHC of MMR proteins

Abstract Background The clonality of primary tumors is well elucidated. In contrast, the relation to metastatic foci is not well understood. We examined genomic clonality of primary tumors and metastatic foci. Method We studied 144 foci (34 primaries, 104 lymph nodes, 6 organ mets) from 10 patients with gastrectomy (c-Stage 3). We also searched the expression of MMR proteins. Results In 10 primaries, mutations were found in all (range 3-12, mean 6). Of 104 lymph nodes, 64 lymph nodes carrying mutations identical to corresponding primaries in all. In addition, all the genomic profiles were replicated in corresponding lymph nodes and visceral mets. Among 3 cases with dMMR, all metastatic foci showed identical phenotypes. Conclusion Surprisingly, significantly mutated genes (SMGs) profiles in all lymph nodes and visceral mets were identical to the primaries. In addition, MMR/MSI status was also identical. These results indicated proper selection of chemo-, molecular-, and immune-oncology treatments could be effectively applied to the spreaded mets. Internoduler ""de novo"" heterogeneity was so scarce. Often claimed tumor heterogeneity could be due to inappropriate selection of drugs and due to their pressure.