What is proton therapy?
Proton therapy is one of the most successful forms of precision radiotherapy. Initially developed to treat tumors of the eye and intra-cranial tumors, proton therapy has expanded considerably throughout the world with a broadening of its indications, particularly in pediatrics, due to the decreased risk of after effects.
Institut Curie has one of two centers in France that is able to administer this ultra-precise form of radiotherapy. Located at the Orsay site, it is the world’s No. 4 proton therapy center.
The advantages of proton therapy
Today, classic radiotherapy uses photon* and/or electron beams. Proton therapy involves a beam of protons – elementary particles that carry a positive charge. It is the energy deposited by these particles that leads to the destruction of the tumor cells.
The particle accelerators found in classic radiotherapy devices generate an electron beam. These charged particles are either used directly to treat the patient, or sent to a target that will create a photon beam, which is then sent to the patient.
Electrons are used routinely for superficial irradiation of a few centimeters in depth. Their physical properties allow them to deposit their energy more deeply. The photon beams deliver a uniform dose that goes deeper. However, this energy deposit is not strictly localized. There is a slight lateral dispersion along the line of administration, related to the shadow of the beam, and a high dispersion before and after the
“maximum dose deposit.”
Although classic radiotherapy has made many significant improvements due to the development of conformal radiotherapy, it has not achieved the ballistic precision of proton beams. There is only one reason for this, namely the specific physical properties of these particles.
First advantage: the protons will cross through the material to deposit almost all of their energy at a given depth, then will stop abruptly. The initial energy of the protons determines the depth reached.
Second advantage: the protons disperse very little along this trajectory. The result is that the areas adjacent to the beams undergo very little collateral damage. The specific, localized energy deposit from protons also offers the option to increase the dose received by the tumor without increasing the dose sent to the healthy surrounding tissue.
With proton therapy, radiotherapists have ultra-precise ballistic radiation, highly useful for treating tumors close to sensitive organs, particularly in children.
*PHOTON: elementary particle, which in the current concept of light constitutes electromagnetic waves, radio waves with gamma rays and visible light.