**3. Epidemiology and etiology of venous thromboembolism**

Among CAT, VTE most often occurs in cancer patients. VTE is a disease that includes deep vein thrombosis (DVT), which usually occurs in the lower legs, and pulmonary embolisms (PE). Most isolated distal DVTs do not extend to the proximal veins and remain uneventful, whereas parts of clot may break off from proximal DVTs and they may cause potentially life-threatening PE. VTE is the third frequent cardiovascular diseases in Western countries next to myocardial infarction and stroke, and it is estimated that annual incidence of VTE is 1–2 per 1000 adults in the USA [6]. Racial differences may exist in the incidence of VTE, and it is reported that the incidence of VTE in whites is five times higher than that in Asians [7]. Previously, the incidence of VTE in Japanese population was supposed to be low, but more Japanese patients have been diagnosed with VTE, recently. The number of patients diagnosed with PE was 28 per 1,000,000 people in 1996, and it increased to 126 in 2011 [8].

There are several risk factors that induce VTE, and cancer is one of the main risk factors for VTE (**Table 2**). It has been reported that cancer is associated with 18% of all VTE, and the overall risk of VTE was increased sevenfold in patients with a malignancy (odds ratio [OR], 6.7; 95% confidence interval [CI], 5.2–8.6) vs. persons without malignancy [9].

**125**

0.3–28% [20].

*Etiology of Cancer Associated Thromboembolism (CAT), and Diet, Lifestyle and Medicine…*

**4. Risk factors for cancer-associated venous thromboembolism**

lymphoma patients than in low-grade lymphoma patients [16, 17].

Incidence rates of VTE increase with age in the general population. Likewise, cancer-associated VTE occurs more often in the elderly population than younger population. Khorana et al. reported that age 65 or older is an independent risk factor for developing cancer-associated VTE. Cancer-associated VTE is more common in female sex and black race [3]. Obesity; complications such as respiratory disease, kidney disease, and infection; and poor performance status are also risk factors for

The risk of VTE varies by cancer site, and meta-analysis of several studies proves that the incidence of VTE is highest in the pancreatic cancer patients, followed by hematological malignancy and brain tumor patients [13]. VTE more often occurs in patients with advanced cancer than in patients with early cancer [14]. The incidence of VTE also varies by cancer histology, is higher in lung adenocarcinoma patients than in lung squamous cell carcinoma patients [15], and is higher in high-grade

Cancer treatment also affects VTE incidence. VTE is a common complication of surgery, regardless of whether it is cancer surgery or not, and adequate prophylaxis is recommended in guidelines including Japanese guideline [18]. However, among cancer patients who received adequate VTE prophylaxis after surgery, 2.1% of them developed massive VTE and 0.8% of them died [19]. Many types of anticancer drugs, such as cisplatin, l-asparaginase, and bevacizumab, also increase risk of thrombosis in cancer patients. Especially, the incidence of VTE is very high in multiple myeloma patients receiving immunomodulatory drugs (e.g., thalidomide, lenalidomide, and pomalidomide), and these patients need primary prevention of VTE by using antithrombotic drugs. Cancer patients often need indwelling central venous catheter (CVC) for delivery of intravenous drugs, parenteral nutrition, and collecting blood samples. Indwelling CVC increases risk of developing VTE, and it is estimated that the risk of symptomatic catheter thrombosis is

Considering these factors, several risk models to predict the occurrence of cancer-associated VTE have been published. Khorana score is the most widely used risk model among them [21]. Five predictive variables are identified in this score: site of cancer (2 points for very high-risk site, 1 point for high-risk site), platelet

*DOI: http://dx.doi.org/10.5772/intechopen.92379*

cancer-associated VTE [10–12].

*Risk factors for venous thromboembolism.*

**Table 2.**

*Etiology of Cancer Associated Thromboembolism (CAT), and Diet, Lifestyle and Medicine… DOI: http://dx.doi.org/10.5772/intechopen.92379*


**Table 2.** *Risk factors for venous thromboembolism.*

*New Insights into Metabolic Syndrome*

improve prognosis of cancer.

(**Table 1**).

**Table 1.**

*Cancer-associated thrombosis.*

**2. History of cancer-associated thrombosis**

of death in cancer patients undergoing chemotherapy after death directly related to cancer [4]. Therefore, it is important to prevent and treat cancer-associated VTE to

French physician Armand Trousseau first described the relationship between cancer and thrombosis when he reported multiple cancer patients complicated with "phlegmasia alba dolens" caused by deep vein thrombosis in 1865 [5]. He speculated that excess of fibrin and hypercoagulable state of blood caused thrombosis in these patients. Two years later, he suffered from "phlegmasia alba dolens," and he died from gastric cancer. Since then, many studies have revealed the relationships between cancer and thrombosis. Presently, it is well known that thrombosis, i.e., venous thromboembolism (VTE), arterial thrombosis, disseminated intravascular coagulation, and thrombotic microangiopathy, often occurs in cancer patients, and thrombosis occurring in cancer patients become to be recognized as cancer-associated thrombosis (CAT)

**3. Epidemiology and etiology of venous thromboembolism**

Among CAT, VTE most often occurs in cancer patients. VTE is a disease that includes deep vein thrombosis (DVT), which usually occurs in the lower legs, and pulmonary embolisms (PE). Most isolated distal DVTs do not extend to the proximal veins and remain uneventful, whereas parts of clot may break off from proximal DVTs and they may cause potentially life-threatening PE. VTE is the third frequent cardiovascular diseases in Western countries next to myocardial infarction and stroke, and it is estimated that annual incidence of VTE is 1–2 per 1000 adults in the USA [6]. Racial differences may exist in the incidence of VTE, and it is reported that the incidence of VTE in whites is five times higher than that in Asians [7]. Previously, the incidence of VTE in Japanese population was supposed to be low, but more Japanese patients have been diagnosed with VTE, recently. The number of patients diagnosed with PE was 28 per 1,000,000 people in 1996, and it increased to 126 in

There are several risk factors that induce VTE, and cancer is one of the main risk factors for VTE (**Table 2**). It has been reported that cancer is associated with 18% of all VTE, and the overall risk of VTE was increased sevenfold in patients with a malignancy (odds ratio [OR], 6.7; 95% confidence interval [CI], 5.2–8.6) vs. persons

**124**

2011 [8].

without malignancy [9].
