Pictured from right: Helge Knudsen and Niels Bassler from the University of Aarhus and the Aarhus University Hospital, respectively, with their American colleague Michael Holzscheiter at the apparatus where the irradiation of cancer cells using antiprotons takes place. The antiprotons come out of the curved metallic film at left, and penetrate the white plastic tube that contains the cancer cells. Following irradiation, the number of surviving cancer cells are observed. This apparatus is set up at the Antiproton Decelerator at CERN.

The results have just been published in the renowned journal Radiotherapy and Oncology.

The mysterious antiparticles have been common knowledge for decades, but the scientists are the first to show the advantage of using antiprotons to destroy cancer cells. The new technique using antiparticles has a number of benefits:

A comparison of damage to the healthy tissue surrounding the tumour shows that antiproton beams destroy cancer cells much more effectively than the beams used to date. This is because the antiprotons have an effect that slightly resembles grenades. They cause most damage to the patient’s cells right at the target point – just as a grenade only explodes when it gets to the end of its trajectory.
Each individual patient therefore requires significantly fewer treatments.
Irradiating cancerous tissue can be carried out with a high degree of spatial precision because it is possible to hit a tumour within areas as small as one cubic millimetre.
An added advantage of antiproton treatment is that it makes it possible to continuously monitor exactly where the irradiation takes place.

Unfortunately, the promising results will first benefit the treatment system in ten years at the earliest. This is partly because producing antiprotons is expensive and requires setting up large, new accelerators specially designed for the purpose. Secondly, a long list of new measurements are required before clinical tests can begin. However, the important point is that the scientists have now proved the significant, positive effect of antiproton irradiation.

This new knowledge itself is an important radiobiological result because the scientists are the first to demonstrate the biological effect of antiprotons. The new knowledge can therefore be used immediately to increase our understanding of how antiparticle beams inactivate cancer cells. As far as the scientists are concerned, the basic scientific insight they have acquired into the biological effect of antiprotons is a major victory in itself, and one that paves the way towards much more cross-disciplinary research. The composition of the research team illustrates the importance placed on interdisciplinary collaboration, as it involves physicists, hospital physicists, doctors, microbiologists and other experts. In addition to the Danish scientists, the team consists of experts from the USA, Canada, Switzerland, the Netherlands and other countries.

The project is funded by the Danish Cancer Society and the Danish Agency for Science, Technology and Innovation.

Antiprotons do not belong to our world

An antiproton is a so-called antiparticle. It is thus part of the mirror world that also consists of the positron – the electron’s antiparticle – as well as other exotic particles. A common feature of them all is that they are not normally found in our world. However, antiprotons are produced in large accelerators at CERN, and have been used there to destroy cancer cells.

The special feature of antiprotons is that their speed can be adjusted so they penetrate the tumour without intruding any further into the patient, and thus cause no further tissue damage. The antiprotons find a normal proton inside the tumour, and this pair is converted to energy and other particles – some of which destroy cancer cells – in a disintegration process.
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