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

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.