Does Xa mark the spot? Monitoring anti-factor Xa in cancer patients receiving low molecular weight heparin.

e23065 Background: For inpatients receiving low molecular weight heparin (LMWH), monitoring anti-factor Xa levels has become a controversial topic given the resource management burden and lack of clear guideline recommendations. Patients with malignancy are at higher risk of experiencing venous thromboembolism (VTE) and major bleeds. However, the American Society of Clinical Oncology does not recommend routine monitoring of cancer patients being treated with LMWH. Patients with cancer encompass a heterogenous group that differ in VTE risk, bleeding risk, and treatment options that affect coagulation. This review seeks to determine if certain subgroups of cancer patients benefit from AFXa monitoring while on LMWH. Methods: A search of the literature was conducted using PubMed and Scopus. The search consisted of a broad set of terms that encompassed "cancer,” “Anti-factor Xa,” and “low molecular weight heparin.” Articles that met the inclusion criteria discussed LMWH utilization in cancer patients, as well as outcomes when monitoring AFXa levels. Results: 561 articles were screened, and 14 articles were included in the review. In 3 of 14 (21.4%) articles, there were separate arms that compared adjusting doses based on AFXa against a control that did not dose-adjust. Of those 3 articles, 1 showed a significant decrease in VTE in the dose-adjustment group. 1 article showed a decrease in VTE in the dose-adjustment group that was not considered significant, though that group did not have any instance of VTE. None of the three articles demonstrated a difference in major bleeds between the two groups. In 5 of 14 (35.7%) articles, the focus was surgical oncology patients. 2 of these 5 articles are mentioned above as having experienced lower rates of VTE in AFXa monitoring groups, though only one was found to be significant. Another article focused on surgical oncology patients found that higher VTE incidence was observed in the group that had subprophylactic dose of AFXa. Another study showed that of the patients that experienced VTE, the mean AFXa level was subprophylactic. Conclusions: This review identified a possible benefit in AFXa monitoring in oncology patients undergoing surgery. The 5 studies that focused on surgical patients could suggest that monitoring AFXa reduces VTE if dose-adjusted to the appropriate range. Certain malignancies, such as pancreatic or hematologic, are considered high risk for VTE. The review did not identify any studies that commented on studying AFXa in the context of these particular high VTE risk cancers. The authors recommend further research in the area of AFXa monitoring and dose-adjustment, particularly in surgical oncology patients and patients with malignancies known to cause VTE at higher rates. Patients with malignancy undergoing surgery may benefit from monitoring AFXa levels while on LMWH, though further investigation is needed.