APOLLO: ATRA plus ATO meets expectations in high-risk APL

All-Trans Retinoic Acid plus Arsenic Trioxide was superior to ATRA-chemotherapy in event-free survival high-risk acute promyelocytic leukaemia.

ATRA plus ATO: first-choice standard therapy for high-risk patients too? 

“ATRA plus ATO is the first-line standard of care for patients with low or intermediate risk APL1,” introduced Dr Uwe Platzbecker (Leipzig University Hospital, Germany) at the start of his talk. “However, in high-risk APL, ATRA plus chemotherapy is still the standard of care and ATRA plus ATO has not yet been assessed.” The phase 3 APOLLO study (NCT02688140) included participants with newly diagnosed high-risk APL (n=133), who were randomised 1:1 to the ATRA plus ATO arm or the ATRA plus chemotherapy arm. The primary endpoint was event-free survival at 2 years follow-up2.

The incidence of relapse at 2 years was significantly higher in the chemotherapy arm than in the ATO arm (14.0% vs 1.6%; P=0.011). Not surprisingly, the 2-year event-free survival rate was higher in the ATO arm than in the chemotherapy arm (88% vs 70%; P=0.02). The overall survival data was not yet mature at 2 years of follow-up but suggested an advantage for participants randomised to ATO (93% vs 87%).

Fewer haematological toxicities in arsenic trioxide-treated patients

“Haematologic toxicities were more prevalent in the chemotherapy arm than in the ATO arm, particularly during the consolidation phase,” evaluated Dr Platzbecker. Thrombocytopenia and grade 3 or 4 neutropenia were almost non-existent in the ATO group during consolidation but were seen in up to 56% of the participants on chemotherapy. The occurrence of non-haematologic toxicities did not differ substantially between the two study arms.

ATRA plus ATO outperformed ATRA plus chemotherapy in participants with previously untreated high-risk APL in terms of event-free survival, a result that may lead to the implementation of ATRA-ATO as a novel first-line standard of care for this population.

Medical writing support was provided by Robert van den Heuvel.

  1. Lo-Coco F, et al. N Engl J Med. 2013;369:111–121.
  2. Platzbecker U, et al. A randomized phase III study to compare arsenic trioxide (ATO) combined to ATRA and idarabucin versus standard ATRA and anthracycline-based chemotherapy (AIDA regimen) for patients with newly diagnosed, high-risk acute promyelocytic leukemia. Abstract #S102, EHA congress 2024, 13–16 June, Madrid, Spain.