Primary Thromboprophylaxis in Ambulatory Pancreatic Cancer Patients Receiving Chemotherapy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Patients with pancreatic cancer (PC) carry the highest risk of venous thromboembolism (VTE) amongst all cancer patients. Appropriate use of primary thromboprophylaxis might significantly and safely reduce its burden. We performed a systematic review of published studies and meeting abstracts using MEDLINE and EMBASE through July 2020 to evaluate the efficacy and safety of primary thromboprophylaxis in ambulatory PC patients receiving chemotherapy. The Mantel-Haenszel random effect model was used to estimate the pooled event-based risk ratio (RR) and the pooled absolute risk difference (RD) with a 95% confidence interval (CI). Five randomized controlled studies with 1003 PC patients were included in this meta-analysis. Compared to placebo, thromboprophylaxis significantly decreased the risk of VTE (pooled RR 0.31, 95% CI 0.19-0.51,p< 0.00001, I-2= 8%; absolute RD -0.08, 95% CI -0.12--0.05,p< 0.00001, I-2= 0%), with an estimated number needed to treat of 11.9 patients to prevent one VTE event. Similar reductions of VTE were observed in studies with parenteral (RR 0.30, 95% CI 0.17-0.53) versus oral anticoagulants (RR 0.37, 95% CI 0.14-0.99) and in studies using prophylactic doses of anticoagulants (RR 0.34, 95% CI 0.17-0.70) versus supra-prophylactic doses of anticoagulants (RR 0.27, 95% CI 0.08-0.90). The pooled RR for major bleeding was 1.08 (95% CI 0.47-2.52,p= 0.85, I-2= 0%) and the absolute RD was 0.00 (95% CI -0.02-0.03,p= 0.85, I-2= 0%). Evidence supports a net clinical benefit of thromboprophylaxis in ambulatory PC patients receiving chemotherapy. Adequately powered randomized phase III studies assessing the most effective anticoagulant and the optimal dose, schedule and duration of thromboprophylaxis to be used are warranted.