Bleeding events in anticoagulated patients with atrial fibrillation (AFib) was strongly associated with a new cancer diagnosis, highlighting the importance of timely investigation of bleeding, according to a study published Feb. 20 in Circulation.

Kavi Grewal, Husam Abdel-Qadir, et al., conducted a population-based cohort study in Ontario, Canada, of patients aged ≥66 years who started on warfarin or direct oral anticoagulants (DOAC) after an AFib diagnosis between 2008 and 2022. Exclusions included patients with valvular disease, chronic dialysis, venous thromboembolism, previous cancer or documented bleeding.

Among the 119,480 patients (mean age, 77.4 years; 52% male), 69.3% received a DOAC and 30.7% received a vitamin K antagonist. At two-year follow-up, 73.0% were still taking an anticoagulant.

Results showed that bleeding was documented in 21.8% of patients (and that 4.9% were diagnosed with a malignancy in the two years after starting anticoagulation. After starting anticoagulation, the median time to bleeding was 266 days and from bleeding to diagnosis of malignancy was 45 days.

After adjustment, patients with bleeding had a fourfold higher risk of any cancer diagnosis. By malignancy site, the hazard ratios (HRs) were 5.0 for gastrointestinal, 5.0 for genitourinary, 4.0 for respiratory, 1.8 for intracranial and 1.5 for nasopharyngeal bleeds. Moreover, for cancers concordant with the bleeding site, the HRs were higher: 15.4 for gastrointestinal, 11.8 for genitourinary, and 10.1 for respiratory.

Notably, only 52.2% of those with malignancy had data on stage of cancer at diagnosis in the Ontario Cancer Registry. Among those patients, more cancers were diagnosed at an earlier stage after bleeding (27.6% stage 4 after bleeding vs. 31.3% without bleeding, p=0.029).

The authors write, "These findings should promote education that timely investigations for malignancy should be considered for people with bleeding after anticoagulation, as they may offer an opportunity for cancer diagnosis at an earlier stage, which may increase the likelihood of cure."