The kinetics of white blood cell and the predictive factors of leukocytosis under oral or intravenous arsenic as the first-line treatment for acute promyelocytic leukemia

We aimed to compare the kinetics of white blood cell (WBC) and explore predictive factors of leukocytosis in non-high-risk acute promyelocytic leukemia (APL), with oral arsenic plus all-trans retinoic acid (ATRA) or intravenous arsenic trioxide (ATO) plus ATRA as a first-line treatment. The absolute count, doubling time and peak time of WBC were analyzed in 64 newly diagnosed non-high-risk APL patients who were treated with different induction regimens containing either oral Realgar-indigo naturalis formula (RIF) (n = 35) or ATO (n = 29). The end points were the dynamic changes of the WBC counts during induction. The time points started at day 1 and were selected over 3-day intervals for 28 days. Among the 64 included patients, the median initial and peak WBC counts were 1.78 × 109/L (range 0.31–9.89) and 12.16 × 109/L (range 1.56–80.01), respectively. The incidence of differentiation syndrome was 9.38%. The dynamic changes in leukocytosis showed a single peak wave in all the patients, and the median time to peak was 10 (range 2–26) days. A higher WBC count was observed in the RIF group than in the ATO group after 10 days of treatment (9.22 × 109/L vs. 4.10 × 109/L, p = 0.015). Patients with the peak WBC count > 10 × 109/L had a shorter WBC doubling time compared to patients with a lower peak WBC (RIF group 4 days vs. 7 days, p = 0.001; ATO group 4.5 days vs. 23 days, p = 0.002). Univariate and multivariable analyses showed that the doubling time of WBC is an independent factor for the peak WBC count. Different kinetics of WBC proliferation were observed during induction with oral arsenic plus ATRA and ATO plus ATRA. The doubling time of WBC is an important independent factor for predicting the peak WBC count.