Prospective Evaluation of Thrombo-Hemorrhagic Events and Hypercoagulation Markers in Patients with Acute Promyelocytic Leukemia (APL) Receiving All-Trans Retinoic Acid (ATRA) Plus Chemotherapy

Introduction: Patients with APL typically present with a life-threatening thrombo-hemorrhagic syndrome (THS), due to the consumption of coagulation factors and platelets, secondary to clotting activation. Presently, all- trans retinoic acid (ATRA) has greatly improved the management of APL, but has not significantly changed the rate of early hemorrhagic deaths and may actually promote thrombosis.Characterizing the coagulopathy and identifying predictive markers of bleeding/clotting complications remain critical issues. Aim: In newly diagnosed APL patients, in the first month after diagnosis, we wanted prospectively to: 1. register thrombo/hemorrhagic events; 2. evaluate, the profiles of circulating hypercoagulation markers and the molecular expression of Tissue Factor (TF), before and during ATRA therapy; and 3. verify whether changes in the biomarker profiles correlate with the occurrence of thrombo-hemorragic events. Methods: Sixty consecutive APL patients receiving ATRA+Idarubicin for remission induction (GIMEMA protocol AIDA2000) were enrolled from January 2005 to March 2017. Blood samples from a subgroup of 30 patients (F/M= 11/19) were obtained at the onset (T0), and on days 7, 14 and 28 (T7, T14, T28) of remission induction therapy. Plasma levels of activated factor VII-antithrombin complex (FVIIa-AT), thrombin-antithrombin complex (TAT), and D-dimer were measured by ELISA; TF mRNA levels in peripheral blood mononuclear cells (PBMC) was evaluated in 16 APL patients by real time-polymerase chain reaction. Results: At enrolment (T0), before starting ATRA, 13.3% of APL patients presented with early major hemorrhages, including 3 (5%) fatal intracranial bleeding and 5 (8.3%) non-fatal major bleeding (i.e. gengivorrhagia, gastrointestinal bleeding, epistaxis, menorrhagia). At T0, the prevalence of thrombosis in the total group of 60 APL patients was 6.6%, including 1 fatal pulmonary embolism (PE), 2 non-fatal venous thrombosis (1 PE, 1 lower limb deep vein thrombosis [DVT]), and 1 non-fatal arterial thrombosis (acute myocardial infarction [AMI]). During ATRA therapy, 8.3% of APL patients developed major bleeding: including 2 fatal intracranial hemorrhage after 3 days of ATRA treatment and 3 non-fatal major bleeding (i.e. gengivorrhagia, epistaxis, menorrhagia) after 7, 10 and 17 days of ATRA. Two more patients developed non-fatal thrombosis (i.e. 1 AMI and 1 DVT) after 9 and 20 days of ATRA treatment, respectively. The laboratory sub-study of 30 subjects showed that, at T0, before starting therapy, the plasma levels of FVIIa-AT, TAT and D-dimer were significantly higher in APL patients compared to controls (p<0.05). During induction therapy with ATRA, the levels of TAT and D-dimer significantly (p<0.05) and progressively decreased at T7 and T14, reaching the lowest value at 28 days. Differently, FVIIa-AT levels were unchanged at T7 and T14, and dropped significantly only at T28 (p<0.05 vs T0). In addition, in APL PBMC from 16 patients, the levels of TF mRNA, initially elevated compared to healthy control PBMC (p<0.05), during induction therapy were significantly decreased by 68% and 90%, at T7 and T28, respectively. In these 16 APL patients, a statistically significant correlation (p<0.05) was found between decrease in TF mRNA and FVIIa-AT levels during ATRA therapy. Of the 30 patients included in the laboratory sub-study, 3 had non-fatal thrombosis at diagnosis, no major hemorrhages were recorded. The predictive value of THS of thrombotic markers could not be calculated. Conclusions: Our data show a significant rate (31%) of severe (fatal and non-fatal) thrombo/hemorrhagic events in our cohort of APL patients in the first 3 weeks of diagnosis, with 4 fatal events (6.6%) occurring early, before starting ATRA. Laboratory data show for the first time that, while TAT and D-dimer confirm to be sensitive to ATRA downregulation, differently FVIIa-AT levels persist at high level over time, showing the perseverance of TF-dependent clotting activation. Future large prospective clinical trials should include FVIIa-AT to evaluate persistent clotting activation during ATRA.