Higher Level of Peripheral Blood CD34 Positive Cells Presented with Unfavorable Prognosis in Intermediate-Low Risk Acute Promyelocytic Leukemia

Our previous work has demonstrated that some acute promyelocytic leukemia (APL) patients had significantly elevated circulating CD34+ cell count (≥ 10 × 10⁶/L), and these patients with higher CD34+ cell level usually presented with high-risk disease (WBC > 10,000/μL). The aim of this study was to investigate whether circulating CD34+ cell count is a prognostic marker in intermediate-low risk APL patients. In this study, 76 intermediate-low risk APL patients and 56 age-adjusted healthy volunteers were evaluated. Enumeration of CD34+ cells was investigated before the treatment. A cut-off value of 10 × 10⁶/L CD34+ cells could just distinguish APL patients with adverse prognostic factors from others and may have the power to predict shorter progression-free survival (PFS) and poor prognosis. Higher count of CD34+ cells was usually associated with nonclassical chromosomal translocation, PML/RARα gene complex fusion, APL history, chemotherapy-related APL, disease progression, second tumor, extramedullary infiltration, FLT3-ITD positive mutation, atypical morphology, BM promyelocyte CD56/CD34 positive expression, myelofibrosis, PCR-positive PML/RARa gene fusion but FISH-negative, marrow necrosis and shorter PFS. Our results suggest that the level of CD34+ cells can be further the stratification of disease risk, a higher CD34+ cell count may be indicative of inferior survival and serve as an adverse biomarker for intermediate-low risk APL.