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.
Proton irradiation was administered to 114 lesions consisting of single or multinodular tumors in 117 patients who were considered either surgically inoperable or medically untreatable. Moreover, the proton-treated 62 of 117 patients with 91 HCC lesions were compared with 42 patients with 65 lesions treated with Lipiodol(R)-targeted chemotherapy (1-TAI) alone during the same period of time, as a control. For the proton therapy only (Monotherapy group), which consisted of 53 lesions in 35 patients, 1-TAI was not given because of advanced preexisting liver cirrhosis, chronic renal failure, or myelodysplastic syndrome. On the other hand, proton therapy combined with 1-TAI which resulted in insufficient accumulation of Lipiodol(R) into the tumors (Combination therapy group), which consisted of 27 patients with 38 lesions, received proton therapy in addition to 1-TAI. Total dose of 75Gy in average was given.
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.
In conclusion, proton therapy is safe and effective, and that it has the special merit of allowing an excellent QOL without any associated complaints throughout the treatment period.