The Association of Extended Venous Thromboembolism Prophylaxis and Venous Thromboembolism After Cancer Surgery.

[BACKGROUND] ASCO recommends extended venous thromboembolism (VTE) prophylaxis with low-molecular-weight heparin (LMWH) or direct oral anticoagulants (DOACs) following cancer surgery. However, these recommendations were based on trials using routine venography, which detects asymptomatic VTEs, and real-life efficacy is not well studied. We aimed to assess the association of extended VTE prophylaxis with the incidence of clinically significant VTE after elective cancer surgery.

[PATIENTS AND METHODS] In this retrospective, population-based cohort study, we identified patients who underwent surgical resection for lung, breast, esophageal, gastric, pancreas, and colon cancer from 2010 to 2017 using the SEER-Medicare linked dataset. Patients were divided into 1 of 2 main groups for comparative analyses: those who received extended VTE prophylaxis after cancer surgery and those who did not. Patients who received extended VTE prophylaxis after cancer surgery were identified as those prescribed prophylactic doses of LMWH or a DOAC within 7 days of discharge, as captured in Medicare Part D files.

[RESULTS] A total of 113,739 Medicare beneficiaries were identified, of whom 1,570 (1.4%) received extended VTE prophylaxis. There was a year-over-year increase in the use of extended VTE prophylaxis during the study period, rising from 0.6% in 2010 to 3.3% in 2017. The overall incidence of VTE was 1.6% at 1 month, 4.3% at 6 months, 5.7% at 12 months, with significant differences observed across cancer types (P<.001). However, patients who received extended VTE prophylaxis had a higher 1-year cumulative incidence of postoperative VTE compared with those who did not (11.4% vs 5.3%; P<.001), an association that was consistent across cancer sites. In adjusted analyses, extended VTE prophylaxis was independently associated with an increased risk of VTE (hazard ratio, 1.6; 95% CI, 1.3-2.0; P<.001). Extended prophylaxis was also associated with a higher 1-year incidence of bleeding events compared with patients who did not receive prophylaxis (12.0% vs 8.5%; P<.001).

[CONCLUSIONS] The utilization of extended VTE prophylaxis after cancer surgery remains low, although it has increased every year. Paradoxically, patients who received extended VTE prophylaxis had higher incidences of clinically significant VTE and bleeding compared with those who did not, likely reflecting patient selection and surveillance bias after surgery. In light of these findings, national guidelines recommending postoperative extended VTE prophylaxis, and its use as a surrogate for quality of care, should continue to be re-examined.