The role of anti–factor Xa in patients with cancer receiving prophylactic low-molecular-weight heparin: a meta-analysis

: Low-molecular-weight heparin (LMWH) is a mainstay in the prevention of cancer-associated thrombosis. However, there is a lack of clear guidelines around routine monitoring of anti–factor Xa (AFXa) levels in cancer patients receiving LMWH for prophylaxis. This study compares fixed versus laboratory-based dosing of LMWH in cancer patients in order to elucidate if there are significant differences in venous thromboembolism (VTE) and bleeding outcomes for this population. To our knowledge, this is the first meta-analysis that evaluates AFXa monitoring specifically in cancer patients. 561 articles were screened, and five studies were included in the meta-analysis. Two studies directly compared outcomes of fixed-dosing versus AFXa-based dosing, and four studies evaluated outcomes based on if AFXa values were subprophylactic, prophylactic, or supraprophylactic. The relative risk of VTE was higher in fixed-dosing versus adjusting for AFXa levels, though this failed to reach statistical significance (RR 9.27, 95% CI: 0.90-95.29, I 2 = 0.0%). Surprisingly, patients with subprophylactic AFXa levels experienced bleeding events at 6% (95% CI: 0.00-0.24, I 2 = 73.3%) compared to 2% at prophylactic levels (95% CI: 0.00-0.08, I 2 = 3.1%), though the difference was not statistically significant. Our findings suggest a lack of benefit in monitoring AFXa in prophylaxis in preventing VTE; however, further investigation into high-risk malignancies or surgical oncology patients in particular may elucidate differences in VTE and bleeding outcomes that guide future prophylactic anticoagulation.