You are here : EN > Science and Society > Radiotherapies


Hadrontherapy versus conventionnal rediotherapy

D'après Revue du Palais de la Découverte (N° 335-336 - février mars 2006) :
Médecine : Cancer : La protonthérapie, une technique d’avenir

Among radiation arsenals, radiotherapy involves sending ionizing radiation to the tumor. The goal is to kill tumor cells while preserving healthy surrounding tissue.
While conventional radiotherapy, initiated a century ago, uses beams of photons or electrons, proton therapy uses beams of protons.
These have advantageous ballistic properties. Unlike X-rays, the proton beams deposit their energy mainly at the end of the path. They do not damage the tissues crossed. In addition, they can target a tumor to the millimeter.

Proton therapy is therefore used to treat cancers located in areas inaccessible to the surgeon's instruments and difficult to treat by conventional radiotherapy because requiring high accuracy. These are cancers in the brain, in areas close to the spinal cord or inside the eye. In such situations, X-rays can damage the tissue they pass through before reaching the tumor.

Protontherapy has now been used for almost 50 years and more than 42,000 patients have been treated worldwide. The most impressive results were obtained in choroidal melanomas, tumors of the eye whose treatment was previously based on removal of the eye.
The implementation of proton therapy however requires heavy technologies: a proton particle accelerator, a radiation protection chamber. In addition, sophisticated devices are required to achieve high precision, acting on the beam conformation, and the exact positioning of the structures treated.

Today, the only French proton therapy centers are those of Orsay and Nice (the latter is limited to eye treatments).
The Orsay Proton Therapy Center, a service of the Institut Curie, is currently undergoing an extension project. The proliferation of proton therapy centers, with a view to applying this technique to a greater number of cancers, would require the development of less heavy and less expensive devices. Researchers from the CNRS and CEA have taken an important step in the exploratory pathways. The devices they are working on use a pulsed laser of high intensity, which, focused on a target, causes the creation of a proton beam. Although still far from clinical requirements, this technique could be an interesting research avenue. Their research was published in Nature Physics. For connoisseurs, they are currently working on the development of a pulsed laser whose pulses would have an energy of about 100 joules (ultrashort pulses) and a duration of a fraction of a picosecond, whose rate is 10 Hz. Such a laser, high power, capable of shooting at high speed, represents a significant technological leap compared to current lasers. The researchers expect to have completed it in two years.
Thanks to this new device, and taking into account the ancillary equipment, a proton-producing installation could then fit in a room (instead of a whole building for a cyclotron): it could be installed in hospitals. Finally, this new device would also be more efficient and less expensive than current installations.
(M.-H. F)