Background and Importance The use of direct oral anticoagulants (DOACs) in cancer patients is complex with frequent drug-drug interactions (DDIs) and suboptimal adherence. We therefore set up hospital-based pharmaceutical consultations dedicated to DOACs in an oncology department.

Aim and Objectives To (i) characterise the prevalence and nature of DDIs and drug-related problems, (ii) assess patients’ adherence rates, and (iii) detect occurrence of overdosing clinical signs among cancer outpatients treated with DOACs.

Material and Methods An observational prospective cohort included cancer patients treated with apixaban or rivaroxaban. Two pharmacist standardised interviews at six months interval were used to assess (a) drug-related problems, (b) patient adherence (Girerd score and medication possession ratio [MPR]) and (c) the occurrence of overdosing clinical signs. Antitumor treatment change between the interviews was an exclusion criterion. Results are presented as mean [minimum-maximum]. Statistical analyses (Paired t-test, McNemar’s Chi-squared test) were performed with R software.

Results 56 cancer patients (28 women, 28 men, mean age: 70 years) were included: 34 outpatients receiving an antitumor treatment and 22 outpatients before their antitumor treatment initiation (mainly chemotherapy (27) and immunotherapy (15)). Their number of medications was 6[0–15]; 15/56 used complementary medicines. They were treated with apixaban (77%) or rivaroxaban (23%) for venous thromboembolism (69%) or atrial fibrillation (27%). 36 patients (64%) were concerned by drug-related problems: side-effects (2/36), under-dosing (2/36), and DDI (32/36), that frequently lead to DOAC monitoring (58%). Of note, 37/56 patients knew no DDI with their DOACs (aspirin…). MPR was 102[40–162]% and Girerd score was 1.2[0–6]. Adherence was optimal (MPR >80% and GIRERD score of 0–1) for 36/56 patients (64%). 24 patients have reported 0.7[0–4] clinical signs typical of overdosing. The second interview was assessed in 18/56 patients (31 excluded patients). There was no statistical difference between the two interviews in patient adherence (p>0.05), knowledge about DDI or signs of DOACs over- or under-dosing (p>0.05).

Conclusion and Relevance Adherence to DOACs seemed optimal in our single-centre cancer patients’ cohort. Pharmaceutical consultations may help to optimise DOACs use with DDI detection in 56% cancer patients and clinical toxicities management. Unfortunately, pharmacist interviews didn’t improve patient knowledge about DOACs. A ‘cancer and thrombosis’ therapeutic education program could be evaluated.

Conflict of Interest No conflict of interest.