Impact of CXCR4 expression on overall survival (OS) and relapse-free survival (RFS) in AML patients. These graphs display Kaplan-Meier estimates of OS (A-B) and RFS (C-D) of AML patients based upon CXCR4 expression on the leukemia cells at time of diagnosis. OS and RFS were calculated for patients with low CXCR4 expression as defined by mean CXCR4 fluorescence intensity ratios (MFIRs) of less than 5 (group A, n=32), intermediate CXCR4 expression with MFIRs of 5 to 10 (group B, n=26), or high CXCR4 expression with MFIRs more than 10 (group C, n=32), as displayed in panels A and C, respectively. Because intermediate and high CXCR4 expression were not significantly different regarding OS and RFS, groups B and C were combined in panels B and D.