Particle physics underlies many medical advances in the fight against cancer.

Suffice it to say that the tenuous connection between the two disciplines did not end there. Whether it’s radiotherapy, magnetic resonance imaging or even radiopharmaceuticals, physics – and particle physics in particular – is driving a range of medical innovations, some of which arise directly from the close collaboration between hospitals, doctors and physicists at CERN in Geneva.

Better images of the human body

If we talk more about this cooperation, the case of oncology is undoubtedly one of the most striking examples. Starting with the advancement of what we call positron emission imaging (PET or PET scan in English), which has now become a common clinical tool for detecting tumors and metastases.

CERN produces about 1,300 different isotopes of 73 chemical elements. For its part, HUG has its own cyclotron, a small accelerator used to produce radioisotopes for diagnostic purposes. “The idea is to use a molecule, such as glucose, and label it with radioisotopes, creating a radiopharmaceutical that will be administered to the patient,” explains Professor Valentina Garibotto, Chief Medical Officer of the Department of Nuclear and Molecular Imaging at HUG. . One of the amazing and unique features of this method is that we can see all the interactions between the radiotracer and the body molecules it targets without damaging healthy tissue.

Flashback to the 1980s. Professor Antoine Geissbühler, Dean of the Faculty of Medicine at the University of Geneva and Director of Teaching and Research at the University Hospitals of Geneva (HUG), was still a medical student when he took up a job in nuclear medicine. HYUG department. Anyone already passionate about computer programming would be far from imagining that this commitment would allow him to collaborate with two renowned physicists: Georges Charpak, winner of the 1992 Nobel Prize for his invention of the multiwire proportional chamber, a new kind of detector capable of recording millions of particle trajectories per second, and David Townsend, recognized for his innovative work in PET imaging and later for the invention of PET-CT, a combination of PET camera and X-ray scanner.

Also read: CERN comes out of the bubble

“Physicists at CERN, including David Townsend, had the idea of ​​using technology developed by Georges Charpak to detect electromagnetic radiation in the context of PET scanning,” describes the Genevan doctor. The result: higher image quality while reducing the required radiation dose. And technology that is making its way into hospitals very quickly, especially at HUG. “Collaboration between CERN and the University Hospitals of Geneva continued for about ten years to continue the development of these instruments,” recalls Antoine Geissbühler. This is an example of successful technology transfer into medicine, which has become history of success a major player in the world of medical imaging.”

Ultra-accurate diagnosis

Let’s stay on the particle detector side, but this time look at the latest advances in nuclear medicine. Goal: Use small amounts of radioisotopes to diagnose and treat cancer. Radioisotopes are isotopes of chemical elements that exhibit nuclear instability, that is, they spontaneously decay and release radioactivity. The lifespan of some is a few fractions of a second, while others are several billion years.

Why is this technique interesting in oncology? “Tumor areas, like infections, increase glucose consumption,” the doctor replies. This way, we can see very small lesions and diagnose tumors at a very early stage, which we would not be able to see with other methods.” Today, dozens of diagnostic radiopharmaceuticals are widely used in the clinic, especially for prostate, thyroid and breast cancer.

Bombarding tumors

In addition, radiopharmaceuticals are also being studied for their therapeutic properties. “Some isotopes produce high energies and have the property of destroying cancerous tissue in which they accumulate,” notes Valentina Garibotto. It’s as if we were bombarding tumor pathology locally. This approach has long been used to treat thyroid cancer. It has also been shown to be more effective than any other cancer treatment approach.”

Other therapeutic radiopharmaceuticals have proven themselves in recent years, such as those that target a molecule called PSMA (prostate-specific membrane antigen). They use the same principle for metastatic prostate cancer, when the patient does not respond to standard treatments. “Publications have shown the advantage of this approach compared to hormonal therapy or chemotherapy. Large-scale studies are ongoing and show promise for use in earlier stages of the disease,” concludes Valentina Garibotto.

Since 2017, a CERN project called Medicis (medical isotopes collected from Isolde) has brought together international collaborations, including French-speaking hospitals and other European institutions, and aims to develop radioisotopes with ideal radiation profiles for medical use. “We have been producing isotopes for nuclear research for more than fifty years, and it happens that some of them have very interesting characteristics for medicine, in particular for new targeted treatments,” recalls Manuela Cirilli, head of CERN’s Medical Applications Unit for Technology Transfer. group. Industry cannot afford to pursue such an approach without already clearly defined commercial prospects as it could prove very expensive, so CERN acts as a bridge. We are not trying to achieve industrial production of these isotopes, but we can provide the technology to institutions that can undertake their production on the required scale.”

Short but powerful emissions

Let’s now move on to particle accelerators. When this term is mentioned, the Large Hadron Collider (LHC) with a circumference of 27 kilometers immediately comes to mind. However, there are smaller accelerators that can be modified to deliver radiation therapy in hospitals.

The principle – the destruction of cancer cells by exposing them to high doses of radiation – has been known for a long time. But in the future it may well prove even more effective. Professor Marie-Catherine Vozenin, head of the Radiation Oncology and Radiobiology Sector at HUG, is one of the pioneers of so-called flash radiotherapy, together with Vincent Favodon from the Institut Curie in Paris. The principle of this concept, discovered about ten years ago, is to irradiate tumors in an ultra-short time, thereby reducing damage to nearby tissue.

“If we could increase the doses received with standard radiation therapy, all tumors could be eradicated,” describes Marie-Catherine Vozenin. Unfortunately, this results in toxicity to healthy tissue. This is currently the main limitation of radiotherapy. With Flash, we were able to show in mouse studies that it is possible to reduce these complications by using beams that can deliver doses in a time on the order of milliseconds, compared to several minutes with the conventional method.”

In collaboration with CERN – and its particle accelerator called Clear – the researcher and her team were able to further increase speed and efficiency, delivering radiation doses in a few nanoseconds (a billionth of a second) and even one picosecond (one trillionth of a second). “Healthy tissues can cope with this very fast radiation, but deteriorating tumors cannot,” adds Marie-Catherine Vozenin.

Feasibility studies are currently being carried out on sick animals, in particular on cats treated at the Zurich Veterinary School for tumors with a poor prognosis. “The experiments show very good antitumor efficacy for all types of tumors and protection for all types of healthy tissue,” the researcher notes. However, in some cases we also see late complications. This tells us the boundaries that need to be defined to be able to move forward and conduct human clinical trials in the future.”

Although it will likely be several years before the technique reaches the clinic, the method is already being imitated as all major cancer centers are developing flash therapy projects, from the United States to Europe, including China and Japan.