Principle of Cancer Radiotherapy

Abstract

Radiotherapy is one of the most common types of nonsurgical anticancer treatment modality, employed in more than 50% of cases. Almost half of cancer patients are cured of their cancer by radiotherapy as part of their anticancer treatment. Radiotherapy kills cancer by the use of ionizing radiation which causes permanent and irreversible double-strand DNA breaks in cancer cells leading to cell death. Unfortunately, it can also kill normal cells leading to acute and chronic treatment-related complications. Traditionally, radiotherapy was seldom employed in the treatment of hepatocellular carcinoma (HCC) because of the risk of severe and sometimes irreversible radiation-induced liver injury (RILD), since a large volume of normal liver which took into account the physiological movement of the liver and the tumors inside during breathing might be irradiated. However, with the advent of new radiation technologies and motion management devices, radiation therapy can now be safely delivered to liver tumors. Further radiation dose escalation in the form of hypofractionated stereotactic body radiation therapy (SBRT) is also now feasible, which delivers a high dose of radiation to the tumors while sparing the adjacent normal organs from unnecessary irradiation, leading to a much better tumor response and favorable safety profile. Furthermore, endovascular radioembolization with radioisotope also produced encouraging results in the treatment of unresectable HCC. In this chapter, we will describe how radiotherapy works in cancer cells and elucidate different types of radiation therapy for HCC.