Caren van Roekel

8 Chapter 1 Although there are many treatment options for colorectal cancer patients with liver metastases, colorectal cancer still remains the second most common type of cancer death worldwide (1). There is a wide variety in colorectal cancer incidence rates: the disease can be considered a marker of socioeconomic development and is more prevalent in countries with a high human development index. In developing countries, such as Russia and China, there is an increase in both incidence and mortality. In long-term developed countries, such as the United Kingdom and Denmark, there is an increase in incidence but a decrease in mortality. In other countries, such as France and the United States, a decrease in both incidence and mortality is seen. The rises in incidence can be explained by a change in dietary patterns (processed meat and alcohol drinks) and lifestyle factors (a sedentary lifestyle), as well as a consequence of screening programs that lead to early detection. The decreases in mortality are due to improved treatment strategies in developed countries (1). The incidence rate increases with age, with the median age worldwide being 66 years. Although the incidence and mortality rates decline for almost all age groups, in high-income countries, they are increasing for individuals younger than 50 years. This is likely due to the change in diet and lifestyle over the past decades, which is first reflected in incidence rates in young age groups. In this patient group, most patients present with advanced-stage disease. For patients with distant-stage disease, the five-year survival rate is only 14% (2). The first site of metastasis is the liver and up to 30% of patients with colorectal cancer develops hepatic metastases (3). For these patients, improved treatment strategies are needed. One of these improved treatment strategies is radioembolization. Radioembolization is a treatment option for patients with primary or secondary liver tumors. The treatment principle consists of the delivery of millions of tiny radioactive microspheres that are injected into the hepatic vasculature via a microcatheter. As hepatic malignancies are fed mainly by arterial blood, the microspheres lodge in small tumor arterioles and selectively irradiate the tumors, while relatively sparing the healthy liver tissue. Treatment is always preceded by a preparatory angiography to map the vascular anatomy and to