[Concurrent proton therapy and chemotherapy for locally advanced cancers]

Charged particles such as protons and carbon-ions offer advantageous physical properties to radiation therapy (RT) for the treatment of various cancers when compared with photons, because they exhibit a spread-out Bragg peak, and may be utilized to achieve a desirable dose distribution to the target volume by using specified beam modulation. Interestingly, the cytocidal effect of protons is almost equal to that of photons, because both protons and photons are considered low-linear energy transfer radiations. Hence, proton beam therapy (PBT) is an attractive RT option, especially in the treatment of locally advanced cancers, as irradiation doses can be safely escalated while sparing the surrounding normal tissues, and because PBT may be concurrently combined with chemotherapy for treating such cancers. Recent advances in PBT techniques including a spot scanning method, as well as an increase in the number of particle therapy institutes are anticipated to yield favorable results through future multi-institutional prospective studies. The University of Tsukuba has carried out several studies to validate the effectiveness of PBT for many types of cancers since 1983. Here, we present our findings on the clinical outcomes of PBT for esophageal cancer, non-small cell lung cancer, intrahepatic biliary tract cancer, pancreas cancer, and bladder cancer; future aspects of PBT concurrently combined with chemotherapy for treating locally advanced cancers are also discussed.