Concomitant administration of asparaginase (ASP) and steroids, the backbone of front line acute lymphoblastic leukemia (ALL) therapy, are shown to increase the risk of thromboembolism (TE). On Dana-Farber Cancer Institute (DFCI) ALL Consortium studies TE is frequent during ASP intensification phase (Consolidation II) where pulse steroids are administered for 5 days at commencement of 3-week multiagent chemotherapy cycles (Grace et al, 2011). These observations indicate that combination therapy with ASP and steroids leads to a hypercoagulable state. However, there are no in vivo or in vitro data to support these clinical observations. Hence we undertook a study to evaluate the impact of concomitant administration of ASP and steroids on markers of endogenous thrombin generation namely prothrombin activation fragment 1.2 (F1.2) and, activated coagulation factor VII (FVIIa) and antithrombin (AT) complex (FVIIa-AT).
ASP administered with steroids results in increased levels of endogenous thrombin generation when compared to baseline or with ASP only therapy.
Children (>1 to ≤18 yrs. of age) treated according to DFCI ALL 05-001 therapy protocol who are in remission following consolidation I therapy, without prior TE or ASP allergy, were eligible. Blood samples collected at 3 time points: prior to the first post-induction dose of E. Coli ASP ("baseline"), prior to Week 2 therapy (effects of ASP and Dex therapy) and prior to subsequent Week 1 (effect of ASP only) of three week cycle of Consolidation II therapy, were analyzed for F1.2 and FVIIa-AT complex. F1.2 levels were estimated by enzyme-linked immunosorbent assay (ELISA). FVIIa-AT levels were analyzed using the Asserachrome FVIIa-AT ELISA kits (Diagnostica Stago). Baseline parameters [time point (TP) 1] were compared to parameters after ASP and Dex (TP2), and after ASP only (TP3) therapy, using paired t-tests. Pearson correlation was used to evaluate the relationship between FVIIa-AT complex and F1.2.
This exploratory study included 9 patients (7 boys; 2 with high-risk ALL). The average age was 4.7 yrs. (range 1 to 8 yrs.). All patients received weekly E. Coli ASP during Consolidation II phase. As shown in Table 1, compared to baseline both F1.2 and FVIIa-AT complex levels were significantly increased at TP2 (ASP and Dex) and TP3 (ASP alone). In all but one patient the FVIIa-AT levels were higher following Dex therapy (TP2) compared to ASP alone (TP3). However this difference was not statistically significant [mean difference 83.4 (SD152.1), 95% CI -33.5, 200.4; p=0.138]. Similarly F1.2 levels were higher at TP2 compared to TP3 in all but 2 patients, but the difference was not statistically significant [mean difference -5.9 (SD 38.2), 95% CI-35.2, 23.4; p=0.656]. Following ASP alone therapy F1.2 and FVIIa-AT were significantly correlated (Pearson correlation coefficient 0.716, p=0.046).
E. Coli ASP and Dex therapy is associated with significantly increased levels of F1.2 and FVIIa-AT levels compared to baseline, indicating activation of the coagulation cascade with increased endogenous thrombin generation. In the majority of patients combination of ASP and Dex had increased levels of F1.2 and FVIIa-AT compared to ASP alone therapy. However as a group this comparison was statistically insignificant. This may explain the increased risk of TE with concomitant ASP and Dex therapy as in Consolidation II phase on DFCI ALL therapy protocol. Small sample size is a limitation of our study. Hence we recommend a larger study to confirm our findings.
Table 1. Variable TP1 Mean(SD) TP2 Mean (SD) Mean Difference TP1/TP2 (SD)[95% CI] P value TP3 Mean (SD) Mean Difference TP1/TP3 (SD)[95% CI] P value FVIIa-AT (pmol/L) 77.4 (25.7) 296.4 (132.3) -291.0 (133.9)[-322.0,-116.0] 0.001 213.0 (131.4) -135.6 (117.6)[-226.0, -45.1] 0.009 F1.2 (nmol/L) 110.7 (45.9) 153.0 (78.8) -42.3 (50.4) [-81.1,-3.6] 0.036 158.9 (80.4) -48.2 (61.3)[-95.3,-1.1] 0.046
No relevant conflicts of interest to declare.