Advantages of particle therapy

Heavy ion radiation is biologically more effective and has a higher destructive power than photon radiation.

Cells dispose of effective mechanisms to repair radiation damage. The reparability of the irradiated tumor tissue is clearly lower after heavy ion radiation compared to photon radiation with the same dose because the damages caused are severer. Heavy ion radiation causes significantly more opposite breaks in both strains of the hereditary molecule (DNA). This closely neighboring double strain breaks can only rarely be repaired by the tumor cells. The consequence is that the DNA breaks into small segments and the tumor cell is no longer able to divide. This is the decisive event leading to destruction of the tumor cell.

Heavy ion radiation destroys also tumor areas with poor blood supply.

The effect of heavy ions encompasses also so-called hypoxic cells suffering from oxygen deficiency. Such cells are found in every tumor in areas with poor blood supply. They are nearly resistant to photon radiation because in order to manifest DNA damage caused by photons on a molecular level, the presence of oxygen is essential that is transported into the tumor via blood circulation.

Heavy ion radiation also destroys slowly growing tumors.

Radiation sensitivity of cells depends on their cell cycle stage. Photon radiation damages nearly exclusively cells in their division phase. For heavy ion radiation, these cell cycle related differences of the cellular radiation sensitivity are very low. Thus, heavy ion radiation may also affect dormant or rarely dividing cancer cells. So it has the potential of destroying also slowly growing tumors that are nearly resistant to photon radiation.

Proton and heavy ion radiation has a wide range in the tissue so that also tumors located deeply in the body receive a sufficiently high, destructive radiation dose.

In the MIT, ions are accelerated to more than three quarters of light speed and the “shot” in a targeted way in direction of the tumor. Depending on the velocity and energy, the ions may penetrate up to 30 cm into the tissue and thus also reach deeply located tumors.

In the context of photon radiation, much energy gets lost on the way through the tissue because of scatter radiation that affects healthy tissue. Photon radiation takes its full effect already in a tissue depth of about only 3 cm. Afterward the radiation dose reduces so that only insufficiently high radiation doses reach deeply located tumors or in case of superficial tumor the tissue behind the tumor is affected. These disadvantages may often be compensated with modern radiation techniques – but not always.

Proton and heavy ions allow Bragg-Peak radiation. The tumor is irradiated with highest precision and the surrounding healthy tissue is optimally preserved.

The healthy tissue surrounding the tumor – and also the tissue located in the radiation canal – is optimally preserved in the context of ion radiation. Due to the high speed and their large mass, the ions most rapidly pass through the tissue and form a clearly delineated beam with only minimal lateral scattering. Only at the end of their way shortly before stopping, ions release their destructive energy to the tissue. Researchers call this area Bragg Peak, named after its discoverer William Henry Bragg (1862-1942; Nobel laureate for physics).

Peak defines the area where radiation reaches is highest value. Afterwards the dose is immediately reduced to nearly zero so that tissue located behind the tumor is not affected. In this way, the therapy beam may be guided so that the maximum radiation dose exactly reaches the tumor. The area of the Bragg Peak can be enlarged optionally by superposing different beams so that tumors of each shape, size, or depth in the tissue are covered by the radiation beam with millimeter precision.

Since precision of radiation with protons and heavy ions ist hat high, a higher radiation dose may be applied. This fact increases the probability of healing.

Generally, every tumor can be destroyed by radiation. The limiting factor is always the healthy tissue surrounding the tumor that must not be damaged. The situation becomes even more complicated when this healthy tissue is extremely radiation-sensitive such as for example brainstem, eye, or gut. Since ion radiation hits that exactly and healthy tissue remains untouched, the radiation dose may be increased of up to 20% in cases of conventional radiation with protons and of up to 35% in cases of heavy ion radiation.