The number of patients treated by proton beam therapy in Japan since 2000 has 
increased; in 2016, 11 proton facilities were available to treat patients. 
Notably, proton beam therapy is very useful for pediatric cancer; since the 
pediatric radiation dose to normal tissues should be reduced as much as possible 
because of the effect of radiation on growth, intellectual development, 
endocrine organ function and secondary cancer development. Hepatocellular 
carcinoma is common in Asia, and most of the studies of proton beam therapy for 
liver cancer have been reported by Japanese investigators. Proton beam therapy 
is also a standard treatment for nasal and paranasal lesions and lesions at the 
base of the skull, because the radiation dose to critical organs such as the 
eyes, optic nerves and central nervous system can be reduced with proton beam 
therapy. For prostate cancer, comparative studies that address adverse effects, 
safety, patient quality of life and socioeconomic issues should be performed to 
determine the appropriate use of proton beam therapy for prostate cancer. 
Regarding new proton beam therapy applications, experience with proton beam 
therapy combined with chemotherapy is limited, although favorable outcomes have 
been recently reported for locally advanced lung cancer, esophageal cancer and 
pancreatic cancer. Therefore, 'chemoproton' therapy appears to be a very 
attractive field for further clinical investigations. In conclusion, there are 
cost issues and considerations regarding national insurance for the use of 
proton beam therapy in Japan. Further studies and discussions are needed to 
address the use of proton beam therapy for several types of cancers, and for 
maintaining the quality of life of patients while retaining a high cure rate.