Clinical Outcomes of Cancer-Associated Thrombosis Beyond 6 Months of Anticoagulation

Introduction Randomized trials of venous thromboembolism (VTE) treatment in cancer have primarily focused on the initial 6-month period and the risk/benefit of additional anticoagulant therapy beyond this time point has not been fully evaluated. Current guidelines recommend continuing full dose anticoagulation after 6 months in patients who have ongoing active cancer and/or those undergoing anti-neoplastic treatment. This recommendation, however, is based on little evidence. Here, we describe clinical outcomes of patients who have completed at least 6 months of anticoagulation. Our aim was to compare VTE recurrence, bleeding rate, and overall survival in patients who continued vs. discontinued anticoagulation after the initial 6-month treatment period. Methods We evaluated a prospective cohort of patients referred to the Cleveland Clinic cancer-associated thrombosis clinic from 8/2014-12/2018. We evaluated clinical characteristics, VTE recurrence, bleeding (major or clinically relevant non-major bleeding (CRNMB) as defined by ISTH criteria), and overall survival in patients who continued vs. discontinued anticoagulation after 6 months. Low-risk for recurrent VTE was defined as not having active cancer and not receiving systemic therapy. Statistical methods included t-tests, chi-squared tests, Cox model, and log rank test where appropriate. Multivariable analysis was performed to analyze outcomes of interest. Results The study population was comprised 284 (73.2%) patients who were followed 6 months after the initial VTE event. Of these, 93 (32.7%) did not continue anticoagulation beyond 6 months, and 191 (67.3%) continued anticoagulation treatment (table 1). Anticoagulation was discontinued for the following reasons: low risk (n=33, 35.5%), bleeding (n=12, 12.9%), clinical decision (n=4, 4.3%) and other including financial reasons (n=43, 46.2%; table 2). In patients who continued anticoagulation, 86/191 (45%) had stage IV disease and the most frequent cancers were hematologic malignancies (58/191, 30.4%) and gastrointestinal cancers (37/191, 19.4%). Low molecular weight heparin was the most commonly prescribed anticoagulant (110/191; 57.6%) followed by direct oral anticoagulants (68/191, 35.6%). There was no difference in the rate of recurrent VTE in patients who remained on treatment beyond six months (23/191; 12%) vs. those who stopped treatment at six months (11/93; 11.8%; p= 0.81; figure 1). In patients who continued anticoagulation 6-12 months after th