We will describe here as clearly as possible to the public the types of cancer therapy, principle of radiotherapy and the cancer therapy using proton beam, a type of radiation. Major approaches to cancer therapy Various types of radiotherapy Proton cancer therapy Irradiation Control Room A check panel of irradiation system on the top; surveillance monitors down below; and further down from left to right, an image reference device, a CT simulator, a CT equipment and an X-ray fluoroscope An irradiation switch and a terminal to input related irradiance conditions Irradiation Room A CT equipment (including lesion positioning) and a bed for CT and treatment Proton beam equipment A bed for CT and treatment being moved to Irradiation Room It is designed to focus the center of a proton beam on the same location determined by CT by moving the bed along the rails on the floor. Major approaches to cancer therapy Currently available major approaches to cancer therapy are "surgery", "chemotherapy" and "radiotherapy". Considering the patient’s social rehabilitation, radiotherapy is achieving the desired effects with respect to QOL (quality of life) improvement, fewer side-effects and healthy organ preservation. To make the most of these effects, it is necessary to advance the development of more effective approach to the therapy. In some cases, radiotherapy is used in combination with “surgery” or “chemotherapy”. [Comparison of major approaches of cancer therapy]   Surgery Chemotherapy Radiotherapy Type and location of the cancer suitable for the approach Advanced cancer from early to medium-stage. The cancer formed in one part of the body. Terminal cancer, malignant lymphoma and leukemia, in general. The cancer spread to the entire body. Advanced cancer from early-stage to surgically inoperable case. The cancer formed in one part of the body. Advantage Highly possible to cure the cancer completely. Possible to halt the progression of the cancer or to prevent pain and symptom. Less likely to lose bodily or organic shapes and functions. Less strain on the entire body. Almost equal possibility to surgery in curing the cancer, if at the early stage. Disadvantage Some risk of losing bodily or organic shapes and functions. May not be available depending on the state of cancer progression, bodily condition or symptom. Low probability of curing the cancer completely. Strong side-effects, likely on the entire body In comparison with surgery, more difficult to cure the cancer in one part of the body if at the advanced stage, and liable to recur. Possible side-effects on the irradiated part of the body. Various types of radiotherapy As for the canter therapy by radiation, various types are available depending on the types of radiation and devices to produce radiation as listed below. Type of radiation Device to produce radiation Feature γ (gamma) - ray Telecobalt radiation source(60Co) Use ofγ-ray emitted from60Co. Potential side-effects on the cells shallow from the body surface such as skin. X-ray Linac (Linear accelerator) Use of X-ray produced by hitting an accelerated electron with Linac on the target. Potential damage to healthy cells between skin and the front of cancer cells, if the cancer developed in a deep part of the body Electron beam Linac (Linear accelerator) / Betatron Use of electron beam accelerated by Linac. Excellent in eliminating the cancer developed in relatively shallow part from the skin. Potential damage to healthy cells between skin and the front of cancer cells, if the cancer developed in a deep part of the body Fast neutron beam Cyclotron Highly effective in destroying cancer cells compared to γ-ray, X-ray and electron beam. Proton beam Cyclotron / Synchrotron Easily targeting cancer cells while avoiding healthy cells. Heavy particle beam Synchrotron Highly effective in destroying cancer cells compared to γ-ray, X-ray and electron beam. Easily targeting cancer cells while avoiding healthy cells. Cancer therapy by γ-ray It is a therapy to destroy cancer cells by the use of γ-rays emitted from radioactive isotope "60Co" (material emitting radiation all the time). Recently, as the imports of 60Co have been stopped and amount of radioactivity at each facility has decreased, fewer facilities are using 60Co because of its less advantage than Linac. Cancer therapy by X-ray and electron beam A commonly used device at general hospitals is called "Linac" and the one with a linear accelerator is in widespread use. This therapy device accelerates X-rays and electrons to destroy cancer cells. In case that cancer cells are located deep in the body as shown in the figure below, however, it has a disadvantage of easily producing side-effects because more radiation hits healthy cells located in front of cancer cells. Cancer therapy by fast neutron beam This therapy had been used at National Institute of Radiological Sciences from 1975 to 1994 in Japan. The therapy has following features; first, it is highly effective in destroying cancer cells compared toγ-ray, X-ray and electron beam, and second, it is effective against cancer cells in a location with thin oxygen (the therapy by X-ray, in general, is not much expected to be effective in the thin oxygen.). As a fast neutron beam spreads into the body in much the same way as X-ray and electron beam, it may cause similar side-effects in case of the cancer located deep in the body. Cancer therapy by proton beam This is the therapy WERC has been working on. Currently in Japan, this therapy is used at Hospital East of National Cancer Center, Proton Medical Research Center of University of Tsukuba, Hyogo Ion Beam Medical Center and Shizuoka Cancer Center, besides WERC. It has the feature of effectively destroying cancer cells located deep in the body, while avoiding healthy cells of shallow parts. Cancer therapy by heavy particle (literally particle heavier than proton, mainly carbon) In Japan, National Institute of Radiological Sciences actually started this therapy in 1994, and it is still used today. Hyogo Ion Beam Medical Center can provide this therapy, too. It has the following features such as; first, effectiveness in destroying cancer cells is higher than X-ray, second, it can effectively destroy cancer cells located deep in the body while avoiding healthy cells, etc. Proton cancer therapy We will describe here the cancer therapy by proton beam which is particularly effective in destroying cancer cells. History of proton therapy The history of proton beam therapy is surprisingly old. It dates from 1946 when Wilson advocated the proton utilization for medical science and Tobias and other researchers treated hypophysis tumor by proton beams at Lawrence Berkeley National Laboratory of University of California. Thereafter, serious clinical studies for proton therapy were started at Uppsala University in Sweden and Massachusetts General Hospital (MGH) of Harvard University in America. Also in Japan, National Institute of Radiological Sciences started clinical studies with 70 MeV cyclotron in 1979, and University of Tsukuba started proton cancer therapy with booster accelerator, a high-energy accelerator, for liver cancer, esophagus cancer, lung cancer and brain tumor as its object diseases. In 1990, a facility for proton therapy was set up in the hospital of Loma Linda University in America, and the therapy was started. Currently, there are many proton therapy facilities being run or to be run all over the world. In Japan, Hospital East of National Cancer Center, Proton Medical Research Center of University of Tsukuba, Hyogo Ion Beam Medical Center and Shizuoka Cancer Center are available. WERC also started proton cancer therapy in FY2001 and is now advancing the clinical studies. Property It is considered that biological effect caused by ionizing radiation is DNA damage. Magnitude of the effect is determined by the amount of ionizing radiation per unit volume which is generated along the track of irradiation. The average energy given per unit track length is called LET (liner energy transfer). The heavier the particles become and deeper they pass into the body, the greater LET becomes. Proton beam belongs to low LET radiation, and its amount is about same as X-ray, γ-ray and electron beam. On the contrary, heavy ion beam, π meson beam, electron beam, etc. belong to high LET radiation. The beam of charged particles such as proton and heavy ion causes Bragg peak, phenomenon in which the energy (speed of particles) becomes lower at a particular depth in the body and the maximum ionization takes place just before it stops. By taking advantage of this phenomenon, it is possible to effectively treat only lesion comparatively in safety, even if the lesion adjoins organs which should be avoided from irradiation. Bragg peak at different energy Proton beam dose distribution / 10MV X-ray dose distribution Proton beam dose distribution           10MV X-ray dose distribution Adaptation and advantage At the proton therapy facilities in the U.S. and Europe, uveal malignant melanoma, prostate cancer, basilar tumor, etc. are mainly irradiated. In Japan, prostate cancer, liver cancer, lung cancer, etc. are mainly irradiated. The difference is because the types of diseases frequently occurred are different between in the U.S. or Europe and in Japan. Proton therapy makes it possible to irradiate lesions which were very difficult to treat by conventional radiotherapies by X-ray or electron, beam and lesions whose functions should be preserved, and it has brought about substantial result in every case. Irradiation method and technique Proton therapy requires very critical therapy planning. Therefore, advanced techniques which make a clear distinction from conventional radiotherapies have been adopted and also under development. The following irradiation techniques are now under development or already in use. Patch field irradiation: This is a useful method for the case of involving a large lesion or the lesion adjoining important organs, and a technique to split the irradiation range into some ranges, or to irradiate from various directions. Breathing synchronous irradiation: This is a technique to irradiate in synchronization with a portion of the breathing phase in case that the irradiated organ moves by breathing like lung and liver. High-precision positioning device: This is a technique to precisely position the target by using fixation devices to lessen shifting error by body displacement, CT and MRI. High-precision 3-D dose distribution calculating system: This is a system to plan the three-dimensional dose distribution appropriately and efficiently based on the image data obtained by CT and MRI. It is necessary to make a plan for delivering enough doses to the target and minimizing to the surrounding important organs. Spot scanning: This is a technique to scan the target in its shape with beams. It delivers enough doses to the target by changing the energy of proton beams and also the depth of the magnified Bragg peak in series. We at WERC have working on researches for advancing proton therapy. Let's watch a proton beam with our own eyes! Proton Therapy Facilities in Japan and Overseas