In this study, EXO1 rs1047840G>A was associated with worse clinical outcomes in lung adenocarcinoma patients after pemetrexed chemotherapy and linked to increased expression of EXO1. Based on our results, it is postulated that the rs1047840-induced change in miRNA binding efficiency may increase the expression level of EXO1, resulting in worse response to pemetrexed chemotherapy and survival outcomes. The gene discussed is EXO1; the disease is lung adenocarcinoma.