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 patients with cancer receiving LMWH for prophylaxis. This study compares fixed vs laboratory-based dosing of LMWH in patients with cancer 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 patients with cancer. A total of 561 articles were screened, and 5 studies were included in the meta-analysis. Two studies directly compared outcomes of fixed dosing vs AFXa-based dosing, and 4 studies evaluated outcomes based on whether AFXa values were subprophylactic, prophylactic, or supraprophylactic. The relative risk (RR) of VTE was higher in fixed dosing vs adjusting for AFXa levels, although this failed to reach statistical significance (RR, 9.27; 95% confidence interval [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%), although the difference was not statistically significant. Our findings suggest a lack of benefit in monitoring AFXa in prophylaxis for preventing VTE; however, further investigation into high-risk malignancies or patients undergoing cancer surgery may elucidate differences in VTE and bleeding outcomes that guide future prophylactic anticoagulation.