Background: Assessment of tumor cell proliferation based on Ki-67 expression yielded conflicting prognostic predictions of patients with diffuse large B-cell lymphoma (DLBCL). The introduction of rituximab to the DLBCL treatment regime has led to alterations in the significance of previous prognostic factors. Methods: We analyzed Ki-67 expression and its correlation with prognosis in 144 patients with DLBCL treated with rituximab plus CHOP (R-CHOP) between July 2003 and January 2008. Results: The complete response (CR) rates following R-CHOP administration were not significantly different, based on Ki-67 expression status (P = 0.104). However, higher rates of relapse were observed in the high Ki-67 expression group (Ki-67 ≥ 85%, n = 46) with 25.0%, compared to 10.0% in the low Ki-67 expression group (Ki-67 < 85%, n = 88) (P = 0.040). The 2-yr event-free survival (EFS) rates were 44.3% and 74.1% in the high and low Ki-67 expression groups, respectively (P = 0.011). The 2-yr overall survival (OS) rate was 66.4% in the high Ki-67 expression group and 82.2% in the low Ki-67 expression group (P = 0.016). In multivariate analysis, Ki-67 expression was a significant prognostic factor for EFS [hazard ratio (HR) = 2.909; 95% confidence interval (CI) 1.261-6.708; P = 0.012]. Ki-67 was associated with OS but with borderline significance (HR = 2.876; 95% CI, 0.972-8.508; P = 0.056). Conclusion: Elevated Ki-67 expression seems to be associated with higher relapse after CR and inferior EFS in patients with DLBCL treated with R-CHOP.
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