Rivaroxaban triggered multifocal intratumoral hemorrhage of the cabozantinib-treated diffuse brain metastases: A case report and review of literature

Brain metastases (BMs) are the most common intracranial malignancy with poor prognosis. Patients with intracranial tumors are at greater risk for thrombotic complications and intracranial hemorrhage. Rivaroxaban is a potent oral anticoagulant with the high selectivity of direct factor Xa inhibition. The incidence and severity of rivaroxaban-triggered intratumoral hemorrhage (ITH) in patients with BMs remain unknown. A 57-year-old woman was diagnosed with multiple lung, bone, and BMs from unknown primary cancer origin, and refused any invasive procedures to confirm tumor pathology. However, this patient had a relatively favorable outcome after treating with cabozantinib, an inhibitor of multiple tyrosine kinases. The patient survived over 2 years and developed deep vein thrombosis of right lower limb. Oral rivaroxaban was prescribed, and the multifocal catastrophic ITH was encountered after 1 week. The last head computed tomography imaging revealed a rare but typical image of diffuse hemorrhagic metastases. Hemorrhagic-prone BMs, therapeutic rivaroxaban, and cabozantinib treatment increase risks to develop ITH. In this case rivaroxaban was the trigger to this terminal event. This case is a miserable lesson and keeps reminding us to stay vigilant in clinical practice even when there is a potential benefit for anticoagulation in such population.

Antithrombotic Effects of Combined PAR (Protease-Activated Receptor)-4 Antagonism and Factor Xa Inhibition

Objective: PAR (protease-activated receptor)-4 antagonism has antiplatelet effects under conditions of high shear stress. We aimed to establish whether PAR4 antagonism had additive antithrombotic activity in the presence of factor Xa inhibition in an ex vivo model of acute arterial injury. Approach and Results: Fifteen healthy volunteers (29±6 years, 7 women) completed a phase zero double-blind randomized controlled crossover trial. Ex vivo platelet activation, platelet aggregation, and thrombus formation were measured following blood perfusion of low shear and high shear stress chambers. Upstream of the chambers, extracorporeal blood was admixed with (1) vehicle, (2) low-dose apixaban (20 ng/mL), (3) high-dose apixaban (80 ng/mL), (4) BMS-986141 (400 ng/mL), (5) BMS-968141 and low-dose apixaban, or (6) BMS-968141 and high-dose apixaban in 6 sequential studies performed in random order. Compared with vehicle, BMS-986141 demonstrated selective inhibition of PAR4-AP (agonist peptide)–stimulated platelet aggregation, platelet-monocyte aggregates, and P-selectin expression ( P ≤0.01 for all). Total thrombus area was reduced under both low shear and high shear stress conditions for all drug infusions ( P <0.0001 for all versus vehicle). BMS-968141 reduced total (≤44.4%) and platelet-rich (≤39.3%) thrombus area, whereas apixaban reduced total (≤42.9%) and fibrin-rich (≤31.6%) thrombus area. Combination of BMS-986141 with apixaban caused a further modest reduction in total thrombus area (9.6%–12.4%), especially under conditions of high shear stress ( P ≤0.027). Conclusions: In the presence of factor Xa inhibition, PAR4 antagonism with BMS-986141 further reduces thrombus formation, especially under conditions of high shear stress. This suggests the potential for additive efficacy of combination PAR4 antagonism and factor Xa inhibition in the prevention of atherothrombotic events.