Abstract Background Direct oral anticoagulants (DOAC) are the standard of care for the prophylaxis of non-valvular atrial fibrillation (NVAF)-cardioembolism, but their use in oncological patients has been limited so far. Methods We retrospectively reviewed the records of the patients referred to two cardio-oncology outpatient units between January 2017 and July 2019, and selected those presenting with NVAF, CHA2DS2-VASc ≥1 for men and ≥2 for women, and cancer on active treatment. The following were considered as contraindications to DOAC: severe chronic kidney disease; anti-neoplastic therapy unknown or with potential moderate-to-severe adverse interactions; cirrhosis or liver metastases. Clinical characteristics of patients on DOAC (group 1), on VKA or LMWH with at least 1 contraindication to DOAC (group 2), and on VKA or LMWH despite not having contraindications to DOAC (group 3) were compared by chi-square or ANOVA. Results Of a total of 3,831 patients, 264 (6.9%) met the inclusion criteria (Figure 1). One-hundred fourteen (43.2%) were in group 1, 61 (23.1%) in group 2 (18 on VKA, 43 on LMWH), and 65 (24.6%) in group 3 (27 on VKA, 38 on LMWH). Anticoagulation was omitted in 24 (9.1%) cases for various reasons: spontaneous bleeding (5), anaemia and/or thrombocytopenia (5), frailty (4), CHA2DS2-VASc 1 (3), pharmacological interactions (1), single episode of NVAF (1); and not clearly motivated in 5 subjects. The only significant difference between the 3 groups was serum creatinine concentration (Table 1). Of note, only 10% of subjects in group 1 received an inappropriate DOAC dose, while LMWH was under-dosed for 18% of patients in group 2 and 31% of patients in group 3 (P=0.002). Conclusions In the setting of a dedicated cardio-oncology consultation, DOAC and VKA are most often appropriately prescribed to cancer patients with NVAF. However, there is residual use of LMWH, not infrequently at non-anticoagulant dosage. This is a non-evidence based common practice in clinical oncology that clearly must be abandoned Figure 1 Funding Acknowledgement Type of funding source: None