Arsenic Trioxide (ATO) Or ATRA For Consolidation Treatment Of Standard Risk Non Elderly Newly Diagnosed APL– Second Interim Analysis Of a Randomized Trial (APL 2006) By The French Belgian Swiss APL Group

ATRA combined to anthracycline-based chemotherapy (CT) remains the classical treatment of newly diagnosed APL, but it is myelosuppressive and may be associated with long-term cardiac toxicity. Both ATO (Powell, Blood 2010) and ATRA (Sanz , Blood 2004) may allow to reduce the amount of CT and further diminish the relapse risk. In a randomized trial (APL 2006 trial), we compared for consolidation treatment ATO, ATRA and Ara C in standard risk APL ( ie with baseline WBC < 10G/L).

In this trial (started in Nov, 2006) newly diagnosed APL patients (pts) < 70 years with WBC < 10 G/L were randomized for consolidation between AraC, ATO and ATRA. The AraC group (standard group) received for induction: ATRA 45mg/m2/d until CR with Idarubicin (Ida) 12 mg/m²/dx3 and AraC 200mg/m2/dx7 started on day 3; first consolidation with the same CT course, second consolidation with Ida 9 mg/m²/dx3 and AraC 1g/m2/12h x4d ; maintenance during two years with intermittent ATRA 15d/ 3 months and continuous 6 MP + MTX,). The ATO and ATRA groups received the same treatment as the AraC group , but AraC was replaced respectively by ATO 0.15 mg/Kg/d d1 to 25 and ATRA 45 mg/m2/d d1 to 15 for both consolidation courses. We present here results of the second interim analysis, made at the reference date of 1st Jan 2012, in 349 pts aged < 70 years included in 78 centers before 2012. The primary endpoint was event free survival (EFS) at 2 years from CR achievement. Relapse, survival, side effects of the treatment and duration of hospitalization were secondary endpoints.

Pre-treatment characteristics were well balanced between the 3 consolidation groups. 347 pts (99.4 %) achieved CR, and 2 (0.5%) had early death. Overall, 3, 0, and 4 pts had relapsed and 5, 2, and 2 pts had died in CR in the AraC, ATO and ATRA consolidation groups, respectively. Two year EFS was 95%, 97.4% and 96.8% (p=NS) and 2 year OS was 96.6%, 97.4% and 99% (p=NS), in the AraC, ATO and ATRA consolidation groups, respectively. Median time to ANC >1 G/L and platelets > 50G/L after the first consolidation course was 24 and 25 days, 24 and 23 days, 17 and 20 days in the AraC, ATO and ATRA group, respectively (p<0.01). Similarly, time to ANC >1 G/L and platelets > 50G/L after the second consolidation course was 23 and 27 days, 19 and 18 days, 13 and 19 days in the AraC, ATO and ATRA group (p<0.01). The overall duration of hospitalization was 60.9, 63.1 and 33 days in in the AraC, ATO and ATRA groups, respectively (p<0.01).

Very high CR rates (close to 98-99%) are now obtained in standard risk APL on a very large multicenter basis using classical ATRA and anthracycline based CT combinations, with very few relapses. ATO or ATRA can replace AraC during consolidation cycles without increasing the relapse risk, and can possibly reduce the rate of deaths in CR (2 and 2 patients versus 5 patients, although the difference was NS). However Ida and ATO, when used concomitantly for consolidation cycles, proved as myelosuppressive as Ida-AraC cycles, while myelosuppression was reduced with Ida-ATRA consolidation courses.

Off Label Use: ATO in the treatment of 1st Line APL.