Prescribing DOACs with specific patient populations in mind

Cancer-associated VTE prophylaxis. VTE prophylaxis for patients with cancer is complex and necessitates a global assessment of cancer location and treatment regimen and setting. Hospitalized patients receiving chemotherapy are at high risk for VTE if mobility is reduced or if other VTE risk factors are present. The International Initiative on Thrombosis and Cancer (ITAC)³¹ and ISTH³² recommend VTE prophylaxis with unfractionated heparin or LMWH (ISTH recommends LMWH more strongly). The 2020 ASCO Guidelines recommend pharmacologic anticoagulation but make no drug-specific recommendation.²⁹ Parenteral treatment in hospitalized patients is not as burdensome as it is in ambulatory patients; therefore, these recommendations are less likely to elicit inpatient opposition.

In the ambulatory setting, patient avoidance of subcutaneous injections necessitates consideration of DOACs for CAT prophylaxis. The Khorana Risk Score (KRS) is a validated tool (scale, 0-7) to predict VTE risk in ambulatory patients receiving chemotherapy.³³ KRS scores ≥ 2 indicate high thrombotic risk and the need for prophylactic anticoagulation. ASCO recommends apixaban, rivaroxaban, or LMWH.²⁹ ISTH and ITAC both recommend apixaban or rivaroxaban over LMWH.^31,34 An RCT published in June 2023 confirmed that, for adults with cancer and VTE, DOACs were noninferior to LMWH for preventing recurrent VTE for 6 months.³⁵ The recommended doses for apixaban (2.5 mg twice daily) and rivaroxaban (10 mg daily) for CAT VTE prophylaxis are lower than FDA-approved treatment doses.³¹

Patients with thrombophilia: VTE prevention

Thrombophilias are broadly categorized as inherited or acquired, with inherited thrombophilia being more prevalent. The Factor V Leiden (FVL) variant affects 2% to 7% of the population, and prothrombin gene mutation (PGM) affects 1% to 2% of the population.³⁶ Other forms of inherited thrombophilia, such as protein C deficiency, protein S deficiency, and antithrombin deficiency, occur less commonly (< 0.7% of the population).³⁶ Antiphospholipid syndrome (APS), the most common acquired thrombophilia, affects approximately 2% of the population.³⁶ APS involves multiple antibodies: anticardiolipin antibodies, lupus anticoagulant, and anti-beta-2 glycoprotein 1 antibodies. Establishing risk for thrombosis across the varying types of thrombophilia has proven difficult, but APS is considered the most thrombogenic thrombophilia apart from extremely rare homozygous inherited thrombophilias.³⁶ Therefore, DOAC recommendations are thrombophilia specific.

Assessing DOAC blood levels is no longer recommended for patients with obesity, as there is insufficient evidence that these measures affect clinical outcomes.

A prospective cohort study evaluated DOACs compared with heparin/warfarin for VTE treatment in patients with inherited thrombophilias.³⁷ Although all 4 available DOACs were included, most patients (61.1%) received rivaroxaban. Patients with an array of inherited thrombophilias, including rare homozygous mutations, were enrolled in this trial. While most patients (66.9%) had a “mild thrombophilia” defined as either FVL or PGM, the remainder had more severe thrombophilias.³⁷ VTE recurrence was similar and uncommon in the DOAC and heparin/warfarin groups, consistent with a previous meta-analysis.³⁸ Surprisingly, an increase in the cumulative risk for bleeding was seen in the DOAC group compared with the warfarin group, a finding inconsistent with prior trials.³⁸ There were no major bleeding events in the DOAC group, but 3 such events occurred in the heparin/warfarin group, including 2 intracranial hemorrhages.

Currently NICE, CHEST, and ISTH do not make a recommendation for a preferred agent in patients with an acute VTE and inherited thrombophilia; however, DOACs would not be inappropriate.^23,28,32 The American Society of Hematology (ASH) had planned to release recommendations related to the treatment of thrombophilia in 2020, but they were delayed by the COVID-19 pandemic.³⁹

APS presents challenges for acute VTE anticoagulation. First, it causes a strongly thrombogenic state necessitating therapeutic anticoagulation. Second, for patients with positive lupus anticoagulant, INR monitoring and standardized INR goals may be inadequate.⁴⁰ Therefore, using fixed-dose DOACs without the need for therapeutic monitoring is appealing, but significant concerns exist for using DOACs in patients with APS.^41-45 ISTH and CHEST recommend warfarin for the treatment and prevention of acute VTE in patients with APS, especially those with triple-­positive (anticardiolipin, lupus anticoagulant, and anti-beta-2 glycoprotein 1) APS.^13,46 Package labeling for all DOACs recommends avoidance in triple-positive APS.^1-4

ASTRO-APS is the most recent RCT to compare apixaban and warfarin for patients with APS,⁴⁷ and it was terminated early after 6 of 23 patients in the apixaban group had thrombotic events, while no one in the warfarin group had such an event.⁴⁸ Subsequently, a meta-analysis⁴⁹ demonstrated that patients with thrombotic APS appear to have a greater risk for arterial thrombosis when treated with DOACs compared with warfarin. These 2 studies may lead to changes in recommendations to avoid DOACs in all patients with APS or may prompt more focused trials for DOAC use in patients with APS plus an antiplatelet to mitigate arterial thrombotic risk.

Continue to: Expanded clinical indications