PB1736 IMPACT OF BCR FUSION TRANSCRIPTS ON OUTCOMES IN ACUTE PROMYELOCYTIC LEUKEMIA (APL)

Background: Acute promyelocytic leukemia (APL) results from fusion of PML RARα gene and accounts for 10% of AML. The breakpoints on chromosome 17 are consistently located in the second intron of the RAR α gene, but on chromosome 15, there are different breakpoint cluster regions, namely bcr1, bcr2, and bcr3 located in intron 6, exon 6, and intron 3, respectively. About 70% of patients with APL have bcr‐1 or long (L)‐type transcript, 20% of patients with APL have bcr‐3 or short (S)‐type transcript, and 10% of patients have bcr‐2 or variant (V)‐type transcript Aims: The primary objective of this analysis was to study patient characteristics and outcomes in relation to bcr fusion transcripts of APL Methods: Data of all patients diagnosed as APL by PCR for PML RARα with known bcr transcripts were retrospectively analysed. Deaths within 72 hours of admission were excluded from the study. Statistical analysis was done using SPSS software, version 25. Overall survival was plotted using the Kaplan‐Meier method Results: A total of 54 patients were analysed. bcr 1, bcr 3, bcr 2 and bcr 2’3 transcripts were seen in 29(53.7%), 20(37%), 3(5.6%) and 2(3.7%) respectively. Ten out of 11 paediatric patients (91%) had bcr1 transcript at presentation. The baseline characteristics and chemotherapy regimens used are tabulated in Table 1. Differentiation syndrome during induction chemotherapy was seen in 6 (21%) and 3 (15%) patients in bcr1 and bcr 3 transcripts respectively. Five patients with bcr3 transcript, 2 patients with bcr1 transcript and one patient each in bcr2 and bcr2’3 transcripts succumbed during induction therapy. Sepsis (45%), followed by DIC (45%) were the most common causes of mortality. At a median follow up of 19 months, the overall survival rate was 93.1% and 74.3 % in bcr1 and bcr3 transcript groups respectively (p = 0.09). Summary/Conclusion: Most of the paediatric patients had bcr1 transcript at presentation. High risk at presentation was significantly higher in bcr3 group. Sepsis and DIC were the most common causes of induction mortality. Patients with bcr3 transcript had nonsignificant inferior survival compared to bcr1