This study aimed to determine the frequency of mouse double minute 2 (MDM2) amplification in esophageal squamous cell carcinomas (ESCC) and to clarify its prognostic significance.
We investigated MDM2 amplification on tissue microarrays, using fluorescence in situ hybridization and analyzed its correlations with clinicopathological features and outcomes in 515 Chinese ESCC patients.
MDM2 amplifications were found in 37 of 515 ESCC patients (7.2%). They were significantly negatively correlated with tumor size (P=0.045), disease progression (P=0.002), and death (P=0.003). Univariate analysis showed that the following clinicopathological factors were associated with disease-free survival (DFS) and overall survival (OS): differentiation (P=0.025 for DFS and 0.061 for OS), vessel invasion (P=0.001 and 0.002), nerve invasion (P=0.009 and 0.001), clinical stage (P<0.001 and <0.001), and MDM2 amplification (P=0.012 and 0.014). Multivariate Cox regression analysis showed that MDM2 amplification was an independent prognostic factor for improved outcomes (P=0.023 for DFS, P=0.027 for OS) and the clinical stage was an independent prognostic factor for poor outcomes (P<0.001). When survival analyses were conducted at different clinical stages, MDM2 amplification was associated with longer DFS and OS in stage I-II ESCC (P=0.003 for DFS and 0.003 for OS), but there was no significant survival difference in stage III-IVa ESCC.
MDM2 amplification was significantly correlated with an improved patient outcome, especially in stage I-II diseases and was verified as an independent prognostic factor in our patients. Therefore, MDM2 amplification may be a potential biomarker for risk stratification of the lower stages of ESCC.

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