e20560 Background: Lung cancer is the leading cause of cancer death worldwide. EGFR tyrosine kinase inhibitors (TKIs) has transformed management in those patients. However, the majority of patients will become resistant to EGFR-TKIs after a period of time. The T790M acquired mutation in exon 20 of the EGFR is the predominant molecular mechanism of acquired resistance. In first-line treatment of global patients with NSCLC, osimertinib had better efficacy compared to first-generation TKIs. In the FLAURA study, the median PFS with first-line osimertinib in Asians was only 16.5 months, compared to 18.6 months in the global population. Moreover, the OS benefit in the Asian population was relatively small. At the same time, the mechanism of resistance to osimertinib is very complex and patients have limited treatment options after first-line osimertinib resistance. A variety of factors can influence the decision for first-line treatment in EGFR mutation-positive patients, including follow-up regimens, the presence of brain metastases, and tolerability, all of which should be considered in the long-term treatment plan. Knowing in advance whether patients are likely to acquire EGFR T790M mutations will help in making treatment decisions. Previous studies have shown that TP53 Arg72Pro polymorphism (rs1042522) is associated with the risk and prognosis of lung cancer. Currently, the association between EGFR mutations and TP53 polymorphisms is unclear, but previous reports have suggested that patients with EGFRmutation demonstrated a higher rate of TP53 mutation than EGFR wild type patients. Therefore, this study aim to explore the association of TP53 polymorphisms (rs1042522) with EGFR T790M acquired mutations, considering the value of T790M in lung cancer treatment. Methods: We analyzed two independent cohorts of patients with EGFR-mutant NSCLC who progressed after first-line EGFR-TKIs treatment from 2013 to 2021 (cohort 1: n=108; cohort 2: n=148). All patients were tested with plasma next-generation sequencing (NGS). Results: The acquired T790M mutation rate was 36%, 30% and 43% in all patients (n = 256), cohort 1 and cohort 2, respectively. Logistic regression analysis showed that TP53 rs1042522 polymorphism was significantly associated with an increased risk of T790M acquired mutation in cohort 1 (GG versus CC: OR (95% CI) = 3.57 (1.15-12.2), P = 0.033) and cohort 2 (GG versus CC: univariable OR (95% CI) = 3.53 (1.30-10.3), P = 0.016; multivariable OR (95% CI) = 2.94 (1.04-8.87), P= 0.047). Conclusions: We found that the TP53 rs1042522 polymorphism GG was associated with EGFR T790M acquired mutations. Knowing in advance whether patients are likely to acquire EGFR T790M mutations will help in making treatment decisions.