Concurrent DOAC, tamoxifen use poses no elevated bleeding risk

In breast cancer patients receiving direct oral anticoagulants (DOACs), tamoxifen is safe to use and does not increase the risk of haemorrhage as compared with concurrent use of an aromatase inhibitor (AI), a study has found.

The study included 4,753 breast cancer patients (mean age 77.4 years, 98.4 percent women) on a DOAC, among whom 1,179 (24.8 percent) were coprescribed tamoxifen and 3,574 (75.2 percent) an AI. The most frequently used DOACs were rivaroxaban (53.2 percent) and apixaban (35.0 percent).

The primary outcome was major haemorrhage requiring an emergency department visit or hospitalization after prescription. Researchers used overlap weighted Cox proportional hazards models, accounting for multiple covariates, to evaluate the risk of haemorrhage in relation to tamoxifen or AI use with a DOAC.

Compared with patients taking tamoxifen, those who were taking AIS were more likely to be younger (mean age, 77.1 vs 78.3 years), with higher Charlson Comorbidity Index (mean, 1.8 vs 1.5) and more advanced cancer stage (stages III and IV: 15.9 percent vs 10.8 percent).

Over a median follow-up of 166 days, the incidence of major haemorrhage while receiving a DOAC was similar in the tamoxifen and AI groups (2.5 percent vs 3.3 percent; 23.4 vs 31.1 per 1,000 person-years). This finding was consistent in weighted models (absolute risk difference, −0.8 percent; hazard ratio [HR], 0.68, 95 percent confidence interval [CI], 0.44–1.06).

Furthermore, there were no significant differences in major or all haemorrhage by DOAC type (p=0.29 and p=0.90, respectively).

The present data provide evidence of the apparent safety of concurrent DOAC and tamoxifen use.