Defining high risk: cost-effectiveness of extended-duration thromboprophylaxis following major oncologic abdominal surgery

Abstract

Purpose: Extended-duration thromboprophylaxis (EDTPPX) is the practice of prescribing antithrombotic therapy for 21 days after discharge, commonly used in surgical patients who are at high risk for venothromboembolism (VTE). While guidelines recommend EDTPPX, criteria are vague due to a paucity of data. The criteria can be further informed by cost-effectiveness thresholds. This study sought to determine the VTE incidence threshold for the cost-effectiveness of EDTPPX compared to inpatient prophylaxis.

Methods: A decision tree was used to compare EDTPPX for 21 days after discharge to 7 days of inpatient prophylaxis with base case assumptions based on an abdominal oncologic resection without complications in an otherwise healthy individual. Willingness to pay was set at $50,000/quality-adjusted life year (QALY). Sensitivity analyses were performed to assess uncertainty within the model, with particular interest in the threshold for cost-effectiveness based on VTE incidence.

Results: EDTPPX was the dominant strategy when VTE probability exceeds 2.39 %. Given a willingness to pay threshold of $50,000/QALY, EDTPPX was the preferred strategy when VTE incidence exceeded 1.22 and 0.88 % when using brand name or generic medication costs, respectively.

Conclusions: EDTPPX should be recommended whenever VTE incidence exceeds 2.39 %. When post-discharge estimated VTE risk is 0.88-2.39 %, patient preferences about self-injections and medication costs should be considered.

Figure 1. Decision Analysis Tree

VTE: Venothromboembolism; DVT: Deep Vein Thrombosis; EDTPPX:Extended Duration Thromboprophylaxis; PE: Pulmonary Embolism; LMWH: Low Molecular Weight Heparin, PTS: Post-thrombotic Syndrome

Figure 2. Cost Threshold for Brand Name LMWH

Cost minimization threshold demonstrating that if VTE probability exceeds 1.2% following discharge from the hospital, extended duration thromboprophylaxis is the preferred cost minimizing option. Cost in 2013 US dollars.

Figure 3. Cost Minimization Threshold for Generic LMWH

. Cost minimization threshold for generic LMWH demonstrating that if VTE probability exceeds 0.2% following discharge from the hospital, extended duration thromboprophylaxis is the preferred cost minimizing option.

Figure 4. Effectiveness Threshold for Extended Duration Thromboprophylaxis by probability of post-discharge VTE

Effectiveness threshold demonstrating that when probability of VTE exceeds 2.5% extended duration thromboprophylaxis with LMWH is the preferred strategy to maximize effectiveness.

Figure 5. Tornado Diagram

C_medication: Cost of medication; p_VTE: Probability of VTE; c_DVT: Cost of DVT; u_LMWH: utility of low molecular weight heparin; c-PE: Cost of pulmonary embolism; u_DVT: utility of deep vein thrombosis; p_DVT: probability of deep vein thrombosis; R_EDTPPX: reduction in venothromboembolism with extended duration thromboprophylaxis; u_PE: utility of PE; p_compliance: probability of compliance.