Liver cancer is the fourth most common malignant tumor in Korea and it is the third most common cause of cancer death worldwide according to the 2009 Korea Central Cancer Registration Annual Report. Excellent survival rate (50-70% 5-year survival rate) can be obtained when surgery is performed including liver transplantation, but most (70-80%) patients with liver cancer are difficult to get surgery due to liver disease associated with cirrhosis. In addition, due to the multi-centric nature of liver cancer in patients with cirrhosis, repeated treatment is required. For these reasons, various treatments for liver cancer (percutaneous arterial embolization, percutaneous ethanol injection, radiofrequency heat therapy, and radiation therapy) have been performed.
Due to recent advances in radiotherapy technology, proton beam therapy (PBT) is a promising treatment for liver cancer because it maximizes radiation to tumor tissues and reduces radiation doses from surrounding normal tissues due to the distinct physical properties of proton beams. Promising therapeutic results and less toxicity have been reported in liver cancer. In addition, several genes in liver cancer (SOCS-1, GSTP, APC, VEGF, PD-EGF, HIF-1, NOS, b-FGF, LINE-1, p27, TOP2A, Ets-1, Bcl-xL, Osteopontin, CD44, etc.) have been reported to be associated with recurrence and prognosis.