All transretinoic acid (ATRA) followed by daunorubicin (DNR)-AraC chemotherapy (CT) has improved the outcome of acute promyelocytic leukemia (APL) by comparison to CT alone. In a randomized trial, (1) we compared 2 induction schedules (ATRA followed by CT [ATRA→CT] and ATRA plus CT [ATRA+CT, with CT added on day 3 of ATRA treatment]) and (2) we assessed the role of maintenance treatment. Four hundred thirteen patients ≤75 years of age and with newly diagnosed APL were included. Induction treatment was stratified on white blood cell (WBC) count and age: patients ≤65 years of age and with an initial WBC count of ≤5,000/μL (n = 208) were randomized between ATRA→CT and ATRA+CT (initially randomized patients); patients with a WBC count greater than (high WBC count group, n = 163) and patients 66 to 75 years of age with a WBC count greater than 5,000/μL (elderly group, n = 42) were not initially randomized and received ATRA+CT from day 1 and ATRA →CT, respectively. All patients achieving CR received 2 additional DNR-AraC courses (only 1 in patients 66 to 75 years of age) and were then randomized for maintenance between no treatment, intermittent ATRA (15 days every 3 months) for 2 years, continuous low-dose CT (6 mercaptopurine + methotrexate) for 2 years, or both, using a 2-by-2 factorial design. Overall, 381 (92%) of the patients achieved complete remission (CR), 31 (7%) suffered an early death, and only 1 patient had leukemic resistance. ATRA syndrome occurred in 64 patients (15%) and was fatal in 5 cases. The CR rate was similar in all induction treatment groups. Event-free survival (EFS) was significantly lower in the high WBC group (P = .0002) and close to significance in the elderly group (P = .086) as compared with initially randomized patients. Relapse at 2 years was estimated at 6% in the ATRA+CT group, versus 16% in the ATRA→CT group (P = .04, relative risk [RR] = .41). EFS at 2 years was estimated at 84% in the ATRA+CT group, versus 77% in the ATRA→CT group (P = .1, RR = .62). Two hundred eighty-nine patients were randomized for maintenance. The 2-year relapse rate was 11% in patients randomized to continuous maintenance CT and 27% in patients randomized to no CT (P = .0002) and 13% in patients randomized to intermittent ATRA and 25% in patients randomized to no ATRA (P= .02). An additive effect of continuous maintenance CT and intermittent ATRA was seen, and only 6 of the 74 patients who received both maintenance treatments had relapsed. Overall survival was improved in patients who received maintenance CT (P = .01), and there was a trend for better survival in patients who received maintenance ATRA (P = .22). Our findings strongly suggest that early addition of chemotherapy to ATRA and maintenance therapy combining continuous CT and intermittent ATRA can reduce the incidence of relapse in APL. This effect already translates into significantly better survival for maintenance treatment with continuous CT.

First results of a randomized trial (APL91 trial) and other randomized or non-randomized studies have shown that ATRA followed by chemotherapy significantly increased event-free survival (EFS) and survival, and decreased the incidence of relapse by comparison to chemotherapy alone in newly diagnosed APL. We present here long-term follow-up of the APL91 trial. In this trial, 101 patients had been randomized between ATRA followed by three courses of daunorubicin-AraC chemotherapy (ATRA group) and the same chemotherapy alone (chemotherapy group). Results were reanalyzed 73 months after closing of patient entry. Updated results of APL 91 trial found a Kaplan-Meier estimate of EFS and relapse rate at 4 years of 63% and 31% in the ATRA group, as compared to 17% and 78% in the chemotherapy group (P = 10 −4 and relative risk 2.95, P = 10 −4 and relative risk 3.68, respectively). Kaplan-Meier survival at 4 years was 76% in the ATRA group and 49% in the chemotherapy group (P = 0.026, relative risk 2.7). In the chemotherapy group, seven of the 27 relapses occurred after 18 months, but no relapse was seen after 43 months. In the ATRA group, four of the 17 relapses occurred after 18 months, including two late relapses (at 58 and 74 months). In the chemotherapy group, 23 of the 25 patients who relapsed achieved a second CR with ATRA, and the Kaplan-Meier estimate of second relapse was 40% at 30 months. In the ATRA group, the 10 patients who relapsed and were retreated with ATRA achieved a second CR. In conclusion, long-term results of APL91 trial confirm the superiority of the combination of ATRA and chemotherapy over chemotherapy alone in newly diagnosed APL, and that ATRA should be incorporated in the front-line treatment of APL. Leukemia (2000) 14, 1371-1377.

All transretinoic acid (ATRA) followed by daunorubicin (DNR)-AraC chemotherapy (CT) has improved the outcome of acute promyelocytic leukemia (APL) by comparison to CT alone. In a randomized trial, (1) we compared 2 induction schedules (ATRA followed by CT [ATRA→CT] and ATRA plus CT [ATRA+CT, with CT added on day 3 of ATRA treatment]) and (2) we assessed the role of maintenance treatment. Four hundred thirteen patients ≤75 years of age and with newly diagnosed APL were included. Induction treatment was stratified on white blood cell (WBC) count and age: patients ≤65 years of age and with an initial WBC count of ≤5,000/μL (n = 208) were randomized between ATRA→CT and ATRA+CT (initially randomized patients); patients with a WBC count greater than (high WBC count group, n = 163) and patients 66 to 75 years of age with a WBC count greater than 5,000/μL (elderly group, n = 42) were not initially randomized and received ATRA+CT from day 1 and ATRA →CT, respectively. All patients achieving CR received 2 additional DNR-AraC courses (only 1 in patients 66 to 75 years of age) and were then randomized for maintenance between no treatment, intermittent ATRA (15 days every 3 months) for 2 years, continuous low-dose CT (6 mercaptopurine + methotrexate) for 2 years, or both, using a 2-by-2 factorial design. Overall, 381 (92%) of the patients achieved complete remission (CR), 31 (7%) suffered an early death, and only 1 patient had leukemic resistance. ATRA syndrome occurred in 64 patients (15%) and was fatal in 5 cases. The CR rate was similar in all induction treatment groups. Event-free survival (EFS) was significantly lower in the high WBC group (P = .0002) and close to significance in the elderly group (P = .086) as compared with initially randomized patients. Relapse at 2 years was estimated at 6% in the ATRA+CT group, versus 16% in the ATRA→CT group (P = .04, relative risk [RR] = .41). EFS at 2 years was estimated at 84% in the ATRA+CT group, versus 77% in the ATRA→CT group (P = .1, RR = .62). Two hundred eighty-nine patients were randomized for maintenance. The 2-year relapse rate was 11% in patients randomized to continuous maintenance CT and 27% in patients randomized to no CT (P = .0002) and 13% in patients randomized to intermittent ATRA and 25% in patients randomized to no ATRA (P= .02). An additive effect of continuous maintenance CT and intermittent ATRA was seen, and only 6 of the 74 patients who received both maintenance treatments had relapsed. Overall survival was improved in patients who received maintenance CT (P = .01), and there was a trend for better survival in patients who received maintenance ATRA (P = .22). Our findings strongly suggest that early addition of chemotherapy to ATRA and maintenance therapy combining continuous CT and intermittent ATRA can reduce the incidence of relapse in APL. This effect already translates into significantly better survival for maintenance treatment with continuous CT.

Summary. In spite of the recent improvement in the outcome of acute promyelocytic leukaemia (APL) with treatment combining all trans retinoic acid (ATRA) and chemotherapy (CT), some patients with this disease still have a poor outcome. The prognostic significance of chromosomal abnormalities in addition to t(15;17) in APL is uncertain. We examined the prognostic significance of secondary chromosomal changes in 292 patients included in a European trial who were treated with ATRA and CT. The incidence of chromosomal abnormalities in addition to t(15;17) was 26% and trisomy 8 was the most frequent secondary change (46% of the cases with secondary changes). No significant differences were seen with regard to age, sex, initial white blood cell count, % of circulating blasts, platelet count, fibrinogen level and incidence of microgranular variants between patients with or without additional rearrangements.Outcome was also similar between patients with t(15;17) alone and patients with t(15;17) and other clonal abnormalities for complete remission (92% vs. 93% respectively), event-free survival at 2 years (76´1% vs. 78´1% respectively), relapse at 2 years (16´7% vs. 11´6% respectively) and overall survival at 2 years (79´9% vs. 79´5% respectively). Analysis according to the type of induction treatment (ATRA followed by CT or ATRA plus CT) or the type of maintenance treatment (with ATRA, lowdose CT or both) also failed to show any difference between the two groups. Thus, in a large cohort of APL patients treated with ATRA and CT, additional chromosomal abnormalities had no impact on prognosis.

In spite of the recent improvement in the outcome of acute promyelocytic leukaemia (APL) with treatment combining all trans retinoic acid (ATRA) and chemotherapy (CT), some patients with this disease still have a poor outcome. The prognostic significance of chromosomal abnormalities in addition to t(15;17) in APL is uncertain. We examined the prognostic significance of secondary chromosomal changes in 292 patients included in a European trial who were treated with ATRA and CT. The incidence of chromosomal abnormalities in addition to t(15;17) was 26% and trisomy 8 was the most frequent secondary change (46% of the cases with secondary changes). No significant differences were seen with regard to age, sex, initial white blood cell count, % of circulating blasts, platelet count, fibrinogen level and incidence of microgranular variants between patients with or without additional rearrangements. Outcome was also similar between patients with t(15;17) alone and patients with t(15;17) and other clonal abnormalities for complete remission (92% vs. 93% respectively), event-free survival at 2 years (76.1% vs. 78.1% respectively), relapse at 2 years (16.7% vs. 11.6% respectively) and overall survival at 2 years (79.9% vs. 79.5% respectively). Analysis according to the type of induction treatment (ATRA followed by CT or ATRA plus CT) or the type of maintenance treatment (with ATRA, low-dose CT or both) also failed to show any difference between the two groups. Thus, in a large cohort of APL patients treated with ATRA and CT, additional chromosomal abnormalities had no impact on prognosis.