How is acute promyelocytic leukemia (APL) treated?

Updated: Sep 12, 2017
  • Author: Mark E Weinblatt, MD; Chief Editor: Jennifer Reikes Willert, MD  more...
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Answer

The discovery of effective maturation agents has altered the approach to treating APL.

All-trans retinoic acid (ATRA) can effectively induce remission in most newly diagnosed APLs with the myelosuppressive effects of chemotherapy. The current treatment approach is to begin therapy with ATRA, followed with several days with an anthracycline to induce remission. For patients with a WBC count of more than 10 X 109 (>10 X 103/microliter), concomitant ATRA and anthracycline are used.

Additional cycles of this combination are used as consolidation chemotherapy. Randomized trials have shown an advantage of maintenance therapy for all patients with ATRA and, particularly, high-risk patients with ATRA in combination with 6-mercaptopurine and methotrexate.

Another approach that is being investigated in clinical trials is the use of arsenic trioxide, which is highly active in newly diagnosed and relapsing APL. It effectively induces remissions in 85% of patients who have a relapse. In a North American Intergroup Study, the introduction of arsenic in consolidation was shown to significantly improve overall outcomes in adults with APL.

Gemtuzumab ozogamicin (withdrawn from US market), or anti-CD33 calicheamicin, is also being tested in patients with APL. The hope is that arsenic and gemtuzumab ozogamicin may reduce exposure to anthracyclines without sacrificing efficacy.

The COG is planning on piloting a trial that will replace an anthracycline course of chemotherapy with arsenic trioxide plus ATRA in order to reduce the anthracycline exposure from an estimated 650 mg/m2 to 350 mg/m2 in standard-risk patients and to 450 mg/m2 in high-risk patients.

Patients with APL and high WBC counts at presentation should not undergo leukophoresis because of an increased risk of bleeding due to activation and degranulation of promyelocytes. Instead, hydration and hydroxyurea can be used, followed by rapid initiation of induction chemotherapy. [14]


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