Mechanisms and management of thrombosis in cancer: focus on gastrointestinal malignancies

Cancer patients have an increased risk of venous thromboembolism, which is their second cause of death after disease progression itself. Several thrombotic risk factors coexist in cancer patients, including the ability of both cancer and tumoral microenvironment’s cells to directly or indirectly activate platelets and the enzymes of the coagulation cascade, resulting in a hypercoagulable state of blood. This narrative review gives an overview of the main mechanisms leading to venous thromboembolism in cancer patients, including the role that platelets and the clotting proteins may have in tumor growth and metastasis. Of note, the hemostatic balance is altered in cancer patients who may, next to a thrombosis tendency, also have an increased risk of bleeding. To highlight the complexity and the precariousness of the hemostatic balance of these patients, we discuss 2 specific gastrointestinal malignancies: hepatocellular carcinoma, which is frequently associated with liver cirrhosis, a condition that causes profound alterations of hemostasis, and colorectal cancer, which is characterized by a fragile mucosa that is prone to bleeding. Understanding the molecular mechanisms of cancer-associated thrombosis may give a unique opportunity to develop new innovative drugs, acting differently on distinct pathways and potentially allowing to reduce the risk of bleeding related to antithrombotic therapies.