Is it better to switch from tinzaparin to apixaban in a patient with large volume saddle PE and suspected lung cancer undergoing Stereotactic Ablative Radiotherapy (SABR), and what is the recommended dose of apixaban?

Switching from Tinzaparin to Apixaban for Large Volume Saddle PE in a Patient with Suspected Lung Cancer Undergoing SABR

For a patient with large volume saddle PE and suspected lung cancer undergoing SABR, switching from tinzaparin to apixaban is appropriate, with the recommended dose being apixaban 10 mg twice daily for 7 days followed by 5 mg twice daily. 1

Rationale for Switching to Apixaban

Apixaban is an appropriate choice for this patient for several reasons:

1. Convenience: Direct oral anticoagulants (DOACs) like apixaban offer greater convenience compared to low molecular weight heparins (LMWHs) like tinzaparin, which require daily injections.

2. Efficacy in Cancer-Associated VTE: Apixaban has demonstrated efficacy in cancer-associated venous thromboembolism (VTE). In the Caravaggio trial, apixaban was non-inferior to dalteparin (another LMWH) for the treatment of cancer-associated VTE without an increased risk of major bleeding 2.

3. Compatibility with SABR: While there are no specific contraindications to using apixaban in patients undergoing stereotactic ablative radiotherapy (SABR), the timing of anticoagulation should be carefully considered in relation to the procedure.

Dosing Recommendations

The FDA-approved dosing for apixaban in VTE treatment is:

• 10 mg twice daily for the first 7 days
• Followed by 5 mg twice daily for at least 3 months 1

This dosing regimen is also supported by clinical guidelines for the treatment of acute VTE, including in patients with cancer 3.

Special Considerations for This Patient

Cancer-Associated VTE

• Cancer is a hypercoagulable state that increases the risk of VTE recurrence and complications
• The presence of a large volume saddle PE indicates a significant thromboembolic event requiring effective anticoagulation
• Apixaban has been specifically studied in cancer patients with VTE and found to be effective 2

SABR Treatment

• SABR is recommended for medically inoperable patients with stage T1-2N0M0 NSCLC or medically operable patients who refuse surgery 4
• There are no specific contraindications to using apixaban during SABR, but coordination with the radiation oncology team regarding the timing of doses may be prudent

Monitoring and Follow-up

• Regular monitoring for signs of bleeding is essential, particularly during and immediately after SABR
• Assess for drug interactions with any medications that may be prescribed as part of the cancer treatment regimen
• Consider dose adjustment if the patient has at least two of the following: age ≥80 years, body weight ≤60 kg, or serum creatinine ≥1.5 mg/dL 3, 1

Potential Pitfalls and Cautions

1. Drug Interactions: Be aware of potential interactions with medications commonly used in cancer treatment. Reduce the apixaban dose by 50% when coadministered with drugs that are combined P-gp and strong CYP3A4 inhibitors 1.

2. Bleeding Risk: Monitor closely for bleeding complications, especially during and after SABR treatment.

3. Renal Function: Assess renal function regularly, as cancer treatments and disease progression may affect kidney function.

4. Temporary Interruption: If invasive procedures are required during treatment, apixaban should be discontinued at least 48 hours prior to procedures with moderate or high bleeding risk, and 24 hours prior to procedures with low bleeding risk 1.

In conclusion, switching from tinzaparin to apixaban with the standard dosing regimen (10 mg BID for 7 days, then 5 mg BID) is appropriate for this patient with large volume saddle PE and suspected lung cancer undergoing SABR, provided there are no specific contraindications such as severe renal impairment or significant drug interactions.