Treatment of new cases of acute promyelocytic leukemia with Arsenic trioxide

Introduction: Arsenic Trioxide is effective and approved for treatment of relapsed or refractory APL cases to ATRA but its effects in new cases of APL is not clear and needs long term follow up to disclose the role of this drug in treatment of APL in combination with chemotherapy/ATRA or alone. Material and methods: we studied 111cases of APL (94 new case and 17 relapsed) diagnosed by morphological criteria and confirmed by cytogenetic and/or RT-PCR for the presence of PML/RARA fusion gene. Arsenic Trioxide was infused as 0.15mg/kg/day doses, until complete remission by morphological criteria or till 60 days. In case of complete remission, after 28 days do rest, 0.15mg/kg/days Arsenic Trioxide was infused for an additional 28 days as consolidation. Also, we studied minimal residual disease by semi-sensitive RTPCR on peripheral blood samples up to a year after complete remission. Results: Complete remission was observed in 95 patients (85.6%) and median time to complete remission was 30 days. There was no significant difference between remission rate in new and relapsed cases. During the induction phase, the most common cause of toxicity and mortality was APL differentiation syndrome (23 cases or 20.7%). Other toxicities were serosistis (7.2%) and hepatotoxicity (19.8%). With a median follow up of 16.5(1-57) months for patients in complete remission, one and two year disease free survival (DFS) was 88.3% and 63.7%, respectively. We observed 24 relapses and 19 of them achieved second complete remission, again by Arsenic Trioxide. Median time to relapse was 17 months (4-33) and median time of second DFS after re-treatment with Arsenic Trioxide was 18 months. We observed a third and fourth remission for some patients, who relapsed, again by Arsenic Trioxide. For patients in complete remission, one and three years survival was 95.5% and 87.6%, respectively. Minimal residual disease was positive in 4 (8.3%) out of 48 cases up to a year after remission induction and 3 of these patients clinically relapsed. Conclusion: Arsenic Trioxide is effective as a first line treatment of APL. Results of Arsenic Trioxide combination with chemotherapy/ATRA needs further study. Also it seems that Arsenic Trioxide is applicable for relapsed patients again and drug resistance is an unusual event.