Abstract 639: Acute promyelocytic leukemia

Abstract Introduction: Acute Promyelocytic Leukemia (APL) accounts for 10%-15% of all acute myeloid leukemia's. The use of All-Trans Retinoic Acid/ Arsenic trioxide (ATRA/ATO) in the treatment regimens of low to intermediate-risk patients has led to remarkable cure rates (~80%). However, treatment guidelines of high-risk patients (WBC count≥ 10 x 109/L) remain unclear and these patients are at an increased risk of relapse. Design: Due to ambiguous treatment guidelines for high-risk APL patients as well as limited options for patients with arsenic resistant disease we sought to analyze clinical outcomes in this subset of patients. We conducted a literature search through Pubmed, EBSCO, and JSTOR to identify original articles that evaluated treatment protocols as well as outcomes for high-risk/refractory APL patients. We also evaluated the literature for clinical data involving patients who had arsenic resistant APL. Only relevant articles from 2000 to 2019 were included. Clinical trials where patients did not receive ATRA/ATO treatment were excluded. High risk patients have an increased mortality and decreased overall survival compared to intermediate and low risk patients. Although early death resulting from bleeding complications remains an important clinical hindrance, cases of arsenic resistant disease are becoming more prevalent. Resistant/refractory APL is a rare occurrence; however, no effective treatment exists to overcome resistance in this subset of patients. Of particular interest is the identification of variant translocations in APL; those that differ from the classical PML-RARA (~95%). 12 non-characteristic rearrangements have so far been described; of these, the ZBTB16-RARA and STAT5b-RARA are the most common variants. Both ZBTB16-RARA & STAT5b-RARA are insensitive to ATRA/ATO combination therapy, leaving these patients with limited options. Clinical outcomes have recently been described in a subset of 13 patients with arsenic resistant disease. Of these 13 patients with arsenic resistant disease, 11 eventually died. Mutations in a particular region of the PML protein have been shown to mediate arsenic resistant disease in both in vitro and in vivo models, suggesting a potential benefit of molecular screening to improve clinical outcomes. Neither ATO nor cytotoxic chemotherapy was successful in inducing remissions in this particular subset of patients. Conclusion: Well-defined treatment guidelines in high-risk APL and the need for alternative agents in patients resistant to ATO therapy are needed to improve clinical efficacy and outcomes. 1. Zhu, H.H.; Qin, Y.Z.; Huang, X.J. Resistance to arsenic therapy in acute promyelocytic leukemia. N Engl J Med 2014, 370, 1864-1866, doi:10.1056/NEJMc1316382. Citation Format: Ravinder Singh Chale, Joaquin J. Jimenez. Acute promyelocytic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 639.