The efficacy of powerful proton radiotherapy for hepatocellular carcinoma

Abstract

Protons can be produced by depriving hydrogen atoms of electrons. When accelerated to a high energy level in an accelelator, protons form an ionized beam with strong penetration power. Unlike the conventional radiation beam, the proton beam has a unique dose distribution. It has a peak area (Bragg-peak) in which rapidly increasing doses are deposited at the end of the beam range defined by the particular beam energy. Therefore, proton therapy has an advantage in that a large dose of radiation can be focused only on the target, with a very limited irradiation of surrounding nontumor tissues. Thus the proton can be used to irradiate cancer while selectively avoiding normal tissues. Therefore, proton therapy is one of the modes of external radiation therapy having a potential almost equivalent to that of surgery in terms of local cure of the lesion.We previously reported that a large dose of proton irradiation can be safely given to patients with hepatocellular carcinoma (HCC) complicated with liver cirrhosis. The aim of this report is to show the efficacy of proton radiotherapy for tracing HCC and to clarify the long-term effects and QOL of this new therapy. Cumulative local tumor control rates were 98.1% for the 1st year, 90.9% for the 3rd year, and 88.1% at 3 years after the completion of irradiation. The overall survival rates were: 48.1% for 3 years and, 37.1% for 5 years. In regard to liver function: the Child-Pugh, Child Pugh A and chronic hepatitis groups had significantly higher survival rates than the Child B and C groups. The Child A and chronic hepatitis groups showed especially have an excellent survival rates such as; 60% for 5 yrs. The cumulative local tumor control rate was significantly higher in the proton groups (Mono and Combination) than in the 1-TAI group. The follow-up survival rate in the proton groups was also significantly higher than that in the 1-TAI group. No patients died of the adverse effects of proton therapy. Excellent quality of life (QOL) was maintained in all the patients treated with proton therapy during the treatment periods.

Results of the first prospective study of carbon ion radiotherapy for hepatocellular carcinoma with liver cirrhosis

“…The Tsukuba Proton Medical Research Center succeeded in achieving high local control rate of 88% at 3 years with combination of lipiodol-targeted transcatheter arterial infusion chemotherapy and proton beam RT (17). The gist of the Fig.…”

“…The limitation in therapeutic efficacy and the occurrence of adverse events such as hepatic failure and impairment of the digestive tract suggest shortcomings in cytocidal activity and the dose distribution of the X-ray beam. However, RT using a proton beam has been credited with marked achievements, mainly because of its excellent dose distribution resulting from well-localized energy deposition at the end of the beam path, called the Bragg peak (17)(18)(19). Carbon ion radiation, used in the current study, is known to possess the Bragg peak and has biologically unique characteristics resulting in a higher cytocidal effect than that of proton beams (20 -23).…”