It is unclear if direct oral anticoagulants (DOACs) are effective and safe alternatives to low-molecular-weight heparin (LMWHs) for the treatment of cancer-associated venous thromboembolism (VTE). We aim to synthesize existing literature that compared DOACs versus LMWHs in this high-risk population.

We conducted a systematic review using EMBASE, MEDLINE and CENTRAL for all observational studies and randomized controlled trials (RCTs) (PROSPERO: CRD42017080898). Two authors independently reviewed study eligibility, extracted data, and assessed bias. Primary outcomes included 6-month recurrent VTE and major bleeding. Secondary outcomes included clinically relevant non-major bleeding (CRNMB) and mortality.

We screened 426 articles, reviewed 25 in full-text, and selected 13 and 2 for qualitative and quantitative synthesis, respectively. Based on a meta-analysis of the 2 RCTs, DOACs had lower 6-month recurrent VTE (42/725) when compared to LMWH (64/727) (RR: 0.65 (0.42-1.01)). However, DOACs had higher major bleeding (40/725) when compared to LMWH (23/727) (RR 1.74 (1.05-2.88)). Similarly, CRNMB was higher (RR 2.31 (0.85-6.28)) for patients receiving DOACs. There was no difference in mortality (RR 1.03 (0.85-1.26)). Observational studies were heterogeneous with high risks of bias but showed recurrent VTE rates consistent with the meta-analysis.

DOACs were more effective than LMWHs to prevent recurrent VTE but were associated with a significantly increased risk of major bleeding as well as a trend toward more CRNMB. The absolute risk differences were small (2-3%) for both primary outcomes and may reflect better compliance with DOACs than LMWHs.