Proton therapy (PT) is a promising tool in modern radiation oncology. Contrary to conventional photon therapy, proton radiation reaches its maximum dose only after a certain penetration depth because of the characteristic physical properties (so-called Bragg peak, see graph below). Once the maximum dose has been reached, the effect of the beam stops abruptly so that the tissue immediately lying behind the tumour experiences no damage.
Therefore, the PT is both particularly suited for deep-seated tumours and radiation-resistant tumours that require a high dose as well as for tumours that are located in the same neighborhood as especially critical and sensitive structures. The immature tissues of children are especially susceptible to radiation-induced side effects and require maximum protection. Also, children often receive combination therapy of intensive chemotherapy in addition to surgery.
Comparative studies on the dose distribution of proton and photon radiation have shown that for a given target volume with protons, about half or even a third of the body volume is charged with ionising radiation. So while sparing the normal tissue and decreasing the side effects, high local tumour control rates and low radiation-induced formation of secondary malignancies are expected.