Venous thromboembolism (VTE) is the second leading cause of death in cancer patients
and affects 5 to 20% of patients with known cancer.[1] The treatment of cancer-associated VTE is challenging because the risk of recurrence
and bleeding is higher in these patients than in other patient groups.[2] One of the explanations for such higher rates was the problematic management of
anticoagulant therapy with the vitamin K antagonists (VKA). Drug interactions, liver
dysfunction and malnutrition often lead to unpredictable responses to VKA, while the
need for invasive procedures and the occurrence of side effects of chemotherapeutic
agents require frequent treatment interruptions that are difficult to manage with
VKA given their slow onset and offset of action. To overcome these limitations, low-molecular-weight
heparin (LMWH) was proposed as a therapeutic alternative in this setting and several
studies have consistently proven its superior efficacy over VKA with similar rates
of major bleeding.[3] Following the recommendations of several international guidelines, LMWH has become
the standard of practice for cancer-associated VTE in many countries. To assess the
impact of this therapeutic shift, den Exter and colleagues have performed a retrospective,
observational study comparing major clinical outcomes in patients with cancer-associated
VTE before and after the recommendation of LMWH as the treatment of choice in this
setting.[4] In this study, while the use of LMWH raised from 23 to 67%, the rates of recurrent
VTE or major bleeding remained unchanged, suggesting that multiple clinical factors
rather than the anticoagulant agent per se contribute to the occurrence of these clinical
outcomes. This report provides important information from an unselected population.
However, these findings should not be overestimated given the design of the study,
which cannot challenge the results of randomized controlled trials, and because major
changes in the treatment of cancer may have affected the baseline risk of VTE and
bleeding in these patients overtime. Some practical advantages with the use of LMWH
remain undisputable, but are now challenged by the direct oral anticoagulants.
