3.7 Validation of the prognostic impact of EVI1 expression by TARGET data
Of 129 pediatric Ph-negative BCP-ALL patients from TARGET database for validation, 63 (48.8%) were male, and the median age was 6 (range 1-18) years. 11.3% (12/106), 14.7% (14/95) and 1.8% (2/111) of patients individually had TEL-AML and E2A-PBX1 fusion gene and MLL rearrangement, and 15.6% (15/96) of patients had high-hyperdiploidy karyotype. Totally, 92 (71.3%) patients relapsed and 72 (55.8%) patients died, and the median follow-up time was 50 (range, 3-122) months.
By performing ROC curve, the EVI1 transcript levels with the maximal Youden index was identified as the cutoff value for grouping. As a result, 94 (72.9%) and 35 (27.1%) patients individually belonged to low EVI1 expression and high EVI1 expression. As shown in Fig. 2C, patients with low EVI1 expression tended to have lower 5-year OS rate compared with the patients with high EVI1 expression (47.2% [95% CI 36.7-56.9%] vs 63.3% [95% CI 44.4-77.4%], P =0.066).
We further analyzed the relationship between EVI1 expression and variables at diagnosis (Table S1). TEL-AML1 fusion gene was significantly related to high EVI1 expression (P =0.0006) and E2A-PBX1 was not related to EVI1 expression, which is similar to our cohort. Whereas, no relationship existed between MLL arrangement and EVI1 expression, which was different from our cohort. Furthermore, platelet count and blast percentage in bone marrow were absent in TARGET data.