There is an association between cancer and thrombotic events such as Ischemic Stroke (IS), and these may be the first manifestation of cancer. We evaluated the presence of cancer in patients with IS anticoagulated correctly.

Retrospective case-control study of patients diagnosed with stroke at our institution between 2016 and 2020.

We define anticoagulation failure as the presence of IS in patients correctly anticoagulated with acenocoumarol or warfarin at INR in range, enoxaparin at a dose of 1mg/kg every 12 hours or direct oral anticoagulants (DOAC) without omission of administration in therapeutic doses.

For the control group, we randomly selected patients with IS in the same time period and age range.

We compared the history of active cancer (defined as diagnosis, metastasis, recurrence or treatment of cancer one year before or after stroke), other backgrounds and etiological diagnosis (according to TOAST scale).

We found 90 anticoagulated patients, of which 47 had anticoagulation failure (33 were men; between 56 and 96 years old; mean age: 75 years). The most common reason for anticoagulation was atrial fibrillation (n = 33). Twenty-six patients were being treated with acenocoumarol or warfarin, 19 with DOAC and 2 with enoxaparin.

Active cancer was observed in 5 cases (10.6%), 4 with previously diagnosed cancer and 1 with subsequent diagnosis.

The control group consisted of 47 patients (28 men, mean age: 74 years); 2 of 47 had active cancer (4.3%).

In anticoagulation failure patients, the presence of cancer-related stroke is more frequent than in the control group. This finding supports the need of a prospective study based on the impact of early detection of cancer and its prognosis