Assessment of the Optimal Timing of Chemotherapy With or After ATRA and the Role of Maintenance

Induction treatment was stratified by age and initial WBC count. Patients ≤65 years of age with a WBC count less than 5,000/µL were randomized to receive the reference ATRA treatment of our previous trial (APL91 trial) {Fenaux, 1993 #2088}, ie, 45 mg/m2/d ATRA followed by CT (ATRA→CT group) or ATRA plus CT (ATRA+CT). In the ATRA→CT group, patients received 45 mg/m2/d ATRA orally until CR, with a maximum of 90 days. After CR achievement, they received a course of 60 mg/m2/d daunorubicin (DNR) for 3 days and 200 mg/m2/d AraC for 7 days (course I). However, course I was added to ATRA if the WBC count was increased to greater than 6,000/µL, 10,000/µL, or 15,000/µL by day 5, 10, and 15 of ATRA treatment, respectively, be-cause, from our experience, patients were at risk of ATRA syndrome above those thresholds{de Botton, 2003 #1127; De Botton, 1998 #1604}. Patients randomized to the ATRA+CT group received the same combination of ATRA and CT, with course I of CT starting on day 3 of ATRA treatment.

Patients with a WBC count greater than 5,000/µL at presentation (irrespective of their age) and patients 66 to 75 years of age with a WBC count ≤ 5,000/µL were not ran-domized but received ATRA plus CT course I from day 1 (high WBC group) and the same schedule as in the ATRA→CT group (elderly group), respectively.

Treatment of coagulopathy during the induction phase was based on platelet support to maintain the platelet count at a level greater than 50,000 /µL until the disappea-rance of coagulopathy. The use of heparin, tranexamic acid, fresh frozen plasma, and fibrinogen transfusions was optional.

CR patients received 2 CT consolidation courses, including course II (identical to course I) and course III, consisting of 45 mg/m2/d DNR for 3 days and 1 g/m2 AraC every 12 hours for 4 days. The elderly group only received course II.

Three to 4 weeks after hematological recovery from this consolidation CT, patients who were still in CR were randomized both to receive or not receive intermittent ATRA (45 mg/m2/d, 15 days every 3 months) and to receive or not receive continuous CT with 6 mercaptopurine (90 mg/m2/d, orally) and methotrexate (15 mg/m2/wk, oral-ly), according to a 2-by-2 factorial design stratified on the initial induction treatment group. Maintenance treatment was scheduled for 2 years. Randomizations for induc-tion and maintenance, stratified on center, were performed through a centralized tele-phone assignment procedure.