Non-O blood type was associated with a time-dependent risk of cancer-associated venous thromboembolism (VTE), according to study results published in the journal Blood Advances.

VTE risk is higher among patients with cancer overall, and ABO blood type in the general population is a risk factor for VTE, the researchers explained. However, the relationship between ABO blood type and cancer-associated VTE risk has been poorly understood.

The study involved patients associated with the prospective Vienna Cancer and Thrombosis Study, which enrolled patients with either newly diagnosed or recurrent cancer. Patients were followed for the primary study outcome of VTE, and subdistribution hazard ratios (SHRs) were calculated to quantify VTE risks by blood type over time and in the context of tumor type. Blood types were categorized as either type O or type non-O for comparisons.

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A total of 1708 patients were evaluated, with a median follow-up of 24 months (IQR, 10 to 24). During this period, VTE occurred in 151 patients (8.8%).

The initial 3 months of follow-up revealed no link between VTE risk and non-O blood type (SHR, 1.00; 95% CI, 0.60-1.67; P =.992). However, during the period from 3 to 24 months of follow-up, an association between non-O blood type and VTE risk became apparent (SHR, 1.79; 95% CI, 1.12-2.85; P =.015).

Additionally, a connection was seen between having non-O blood type and the risk of VTE with tumor types considered to be associated with low to intermediate thrombotic risk (SHR, 1.73; 95% CI, 1.09-2.73; P =.019). Non-O blood type did not appear associated with higher VTE risk in the setting of very high-risk tumor types, such as pancreatic, gastroesophageal, or glioblastoma (SHR, 0.94; 95% CI, 0.55-1.61; P =.824).

Non-O blood type was associated with higher levels of von Willebrand factor antigen and factor VIII activity (P <.001 for each). In a multivariable model that adjusted for factor VIII levels, the apparent relationships between non-O blood type and VTE risk were less robust for both the follow-up period of 3 or more months (adjusted SHR, 1.47; 95% CI, 0.92-2.36; P =.109) and with low- to intermediate-risk tumor types (adjusted SHR, 1.59; 95% CI, 0.99-2.55; P =.057).

The research team concluded that cancer-associated VTE risk was higher in patients with non-O blood type and that evaluating blood type may aid in predicting VTE risk in patients with cancer. They also suggested that elevated factor VIII levels may be a contributor to VTE risk associated with non-O blood type. However, they noted that the number of samples available for analysis was limited in this study, so further research is needed to evaluate this possibility.

“ABO blood type group is an easily accessible VTE predictor that can help in the clinical practice during risk assessment in patients with cancer,” the researchers concluded.


Englisch C, Moik F, Nopp S, Raderer M, Pabinger I, Ay C. ABO blood group type and risk of venous thromboembolism in patients with cancer. Blood Adv. Published online April 13, 2022. doi:10.1182/bloodadvances.2021006283