Leukocytosis and retinoic acid syndrome in patients with acute promyelocytic leukemia treated with arsenic trioxide.

Objective: To study the incidence of leukocytosis and retinoic acid (RA) syndrome in newly diagnosed and relapsed acute promyelocytic leukemia (APL) patients treated with arsenic trioxide (ATO).
Methods: Thirty patients with newly diagnosed or relapsed APL received ATO for remission induction at the dose of 10 mg/d. RA syndrome was defined when patient was with one or more of the following signs or symptoms: fever, dyspnea, serous cavity effusion, muscular pain, pulmonary infiltration, weight gain, or pulmonary infiltration on chest X-ray.
Results: Twenty-three (77% ) patients achieved complete remission, mean time to remission was 37.1 days. Leukocytosis was observed in 14 (47%) patients, mean time to leukocytosis was 12.7 days, median baseline leukocyte count for patients with leukocytosis was 3.1 x 10(9)/L, which was higher than that for patients who did not develop leukocytosis (2.6 x 10(9)/L, z = -2.635, P = 0.008). No other cytotoxic therapy was administered, and the leukocytosis resolved in all cases. The RA syndrome was observed in 9 (30%) patients, mean time to diagnose of RA syndrome was 13.9 days, median baseline leukocyte count for patients with RA syndrome was 3.6 x 10(9)/L, which was higher than that for patients who did not develop RA syndrome (2.6 x 10(9)/L, z = -1.909, P = 0.046). No patient died of RA syndrome.
Conclusion: Leukocytosis and RA syndrome are associated with ATO and baseline leukocyte count respectively, and there is distinct link between leukocytosis and RA syndrome.