**Abstract**

Cancer poses the highest clinical and social burden throughout the world and is the second cause of death after is chemic heart disease, although will be predicted the first in 2060. Cancer patients are high risk for thrombotic events that are characterized as the second cause of death after cancer itself. Thrombotic events seem to be increasing over recent years according to improved patients survival, novel thrombogenic cancer treatment and central catheter using. As we know thromboprophylaxis reduces the risk of VTE and primary prevention seems to be more effective way to reduce morbidity and mortality in these patients several criteria was designed to reduce this risk. Khorana risk score is the most important of them which designed for ambulatory cancer patients. Some other risk factors for thrombotic events consist of major abdominal surgery and prolonged immobility after surgery, use of thrombogenic medications (chemotherapy agents), old age, obesity, distant metastasis or advanced stage at the time of diagnosis, hyperthermic intraperitoneal chemotherapy (HIPEC) as a new surgery technique, anemia that requires blood transfusion that recommend special attention should be paid to them.

**Keywords:** cancer, cancer-associated thrombosis, thromboprophylaxis, Khorana score, venous thromboembolism, arterial thromboembolism, cardiotoxicity, cardiooncology

## **1. Introduction**

Cancer poses the highest clinical and social burden throughout the world which is nonsignificantly higher in men than women. The risk of developing cancer is 20.2% for lifelong (22.4% in men and 18.2% in women). Cancer is the second cause of death after ischemic heart disease, although it will be predicted the first in 2060 [1]. The Studies demonstrated 19.3 million new cancer patients and about 10 million cancer deaths occurred in 2020 [2].

Breast cancer has recognized as the most common malignancy followed by lung, liver, colorectal, prostate, and stomach cancers [1, 2]. Despite breast cancer prevalence outstrip lung cancer over the time, the most common causes of death include lung, liver, and stomach cancers, respectively [2, 3].

Thrombus can involve either veins or arteries and is associated with substantial morbidity and mortality as the third most common cardiovascular disease [4]. Acute vein and artery thrombosis is computed as the most common causes of death in developed country. The epidemiology of thrombus depends on if it is venous versus

arterial, provoked versus unprovoked, or first episode versus subsequent episode. Thrombus etiology is multifactorial [5]. Main components of thrombus consist of fibrin, platelets, red blood cells (RBCs), leukocytes [6]. Thrombosis occurs with low shear flow and intact endothelial wall in veins and is associated with severe shear, damaged endothelial wall, and platelet-rich clot formation in arteries [4]. Vein thrombosis is more common due to low velocity of venous blood flow. Sedentary lifestyle, immobilization, contraception agents, pregnancy, surgery, coagulation disorders, high haematocrit level and increased blood viscosity, varicose veins, obesity, infectious disease, and using intravenous drug can contribute to it [4].

Vein or artery thrombus can break away and be transferred to lung or cerebral and peripheral vessels, respectively. Thus, it is important to protect thrombus formation or be diagnosed and start adequate treatment as soon as possible [4].

Cancer patients are high risk for both venous and arterial thromboembolism that are characterized as the second cause of death after cancer itself. Malignancies are responsible for about 18% of all cases with venous thromboembolism (VTE) [7, 8]. Venous thrombosis prevalence in patients with cancer is four- to sevenfold higher compared to healthy individuals [8], and some research reported this risk may be increased up to 28-fold in certain malignancies [7]. A study showed that arterial thrombosis assigns about 5.6% of death in cancer patients. Thrombotic events seem to be increasing over recent years according to improved patients survival, novel thrombogenic cancer treatment, and using central catheter. Venous thromboembolism (VTE) in cancer patients is not limited to deep veins and pulmonary embolism, unusual sites of thrombosis are reported such as upper extremities and cerebral or splanchnic veins. Arterial thromboembolism (ATE) also manifests as myocardial infarction (MI) or cerebrovascular accident (CVA) predominantly [8].
