This is a single-arm prospective observational study aiming to explore the safety and efficacy of switching from direct oral anticoagulants (DOAC) to low molecular weight heparin (LMWH) in cancer patients with atrial fibrillation (AF) during antineoplastic therapy or for a maximum time period of 6 months.~AF is the most common sustained arrhythmia; it affects 1.5% to 2% of the general population, and this prevalence increases to 10% at 80 years of age and to 18% at 85 years of age. Given the increasing occurrence of malignancies in the elderly and the coexistence of other conditions predisposing to AF in cancer patients, an association between those 2 conditions would be expected. A study including 24,125 patients estimated a prevalence of AF of 2.4% at the time of cancer diagnosis. A recent prospective study of 34,691 middle-aged women without AF or cancer at baseline showed that new-onset AF was a risk marker of subsequent diagnosis of cancer (HR 1.48, 95% CI 1.25 to 1.75; p <0.001).~Moreover, patients with cancer are at significantly higher risk of developing venous thromboembolism (VTE) which sometimes may precede the diagnosis of the malignancy. The risk is even higher when the patient is poorly mobilized or hospitalized. On the other hand, some anticancer therapies and especially the novel angiogenesis inhibitors are associated with increased thrombogenicity.~According to current Guidelines, DOACs are preferred over vitamin K antagonist (VKA) therapy and LMWH in both AF and VTE in the general population. However, in the presence of active cancer the administration of LMWH is advised for patients who are hospitalized for any reason and/or receiving chemotherapy, unless there is a high bleeding risk. LMWH has more favorable outcomes in cancer patients than VKAs, both in the setting of primary or secondary thromboembolic prophylaxis while extended anticoagulation (beyond the first 6 months) may be considered for an indefinite period or until the cancer is cured. This is possibly related with the fact that LMWH present antitumour and antimetastatic effects and confer an increased survival benefit. It should be noted that currently there is no conclusive evidence regarding the safety and efficacy of DOACs in cancer patients and the first results seem contradictory.~A number of recent studies with the use of DOACs in cancer-associated venous thromboembolism have demonstrated that these drugs are effective with similar rates of recurrent VTE but higher rates of major bleeding compared to LMWH. However, there are particular disadvantages, especially during the period of chemotherapy, such as interactions between these agents and anticancer therapies (eg, potential interactions between DOACs and azole-antimycotic agents), as well as unknown pharmacokinetics from chemotherapy-related vomiting.~Putting things together, many patients who are under a DOAC due to AF or previous VTE/pulmonary embolism (PE) may be diagnosed with cancer. Moreover, the risk of VTE is 6-fold higher on intravenous chemotherapy. For this reason, current clinical practice suggests that LMWH is continued during treatment with intravenous chemotherapy. However, data on the efficacy and safety of this common approach is lacking. This is important, especially in the setting of gastrointestinal tumors (especially gastric and pancreatic disease) which pose a high bleeding risk and especially during the chemotherapy active period.
The primary objective is to assess the safety and efficacy of switching from direct oral anticoagulants to low molecular weight heparin in cancer patients during antineoplastic therapy