CERN70: From physics to medicine

When the first patients were treated at CNAO, I felt that I'd done very interesting things in physics, but hadron therapy was the best thing I'd done in my professional life.
Ugo Amaldi

Ugo Amaldi was well known as a particle physicist at CERN when he decided to work towards the creation, in Europe, of a network of centres for cancer therapy using beams of ions, in particular carbon ions.

"My interest in medical physics dates back to the late 1950s, when I began to work at Italy's national health institute in Rome, the Istituto Superiore di Sanità (ISS), and wrote a 700-page treaty entitled Fisica delle Radiazioni. I went to ISS instead of starting an academic career because my father Edoardo, a well-known physicist and one of CERN's founders, had been a professor in Rome since 1937 and I wanted to distinguish myself from him.

At the ISS physics laboratory, I performed experiments in nuclear and particle physics and worked part-time in radiation physics and radiotherapy, a subject that I really enjoyed. From 1968 to 1973, I led a group of physicists from ISS working at CERN, and then - after a successful experiment at the Intersecting Storage Rings that discovered the increase with energy of the proton-proton cross-section - in 1973, I was offered a staff position at CERN. One thing led to another and, by 1981, I had initiated and become the spokesperson for DELPHI, one of the four LEP experiments.

By 1991, following the first results and a much-quoted paper on the supersymmetric unification of the fundamental forces, DELPHI was running very well. But it wasn't obvious to me what I should do next. I was 57 years old and I knew I wouldn't be an active experimental physicist when the LHC came online. Still, I wanted to do something new and directly useful at the frontier of what could be done with particle accelerators. I therefore decided to go back to radiation physics; a few years later, my wife Clelia said, "You went back to your first love".

In fact, the idea of using physics to help cure people still appealed to me so, in 1991, I wrote, with Giampiero Tosi, a well-known Italian medical physicist, a proposal for a cancer therapy centre based on beams of carbon ions (and of protons), a treatment modality that, shortly after, I called "hadron therapy". One year later, we created the TERA Foundation to raise funds to cover personnel costs for the design of this centre, for which we received help from the Italian Institute for Nuclear Physics (INFN).

Then, as now, the main tool for cancer therapy was radiotherapy with X-rays, but dedicated proton centres were also being built. However, I was interested in some results obtained at the Lawrence Berkeley Laboratory and in papers written by Gerhard Kraft of GSI. About 1% of tumours treated with X-rays (about 3000 per million people) turn out to be resistant to both X-rays and protons, but it appeared that these stubborn tumours might respond if they were bombarded with the nuclei of carbon atoms. Each carbon nucleus leaves 20 times more energy than a proton in a cell and thus produces multiple, irreparable breaks of the DNA double helix. For this reason, carbon beams are effective in controlling "radioresistant tumours", such as soft-tissue sarcomas, bone sarcomas and some cancers of the brain, lung and salivary glands.

At the end of 1995, with Meinhard Regler of MedAustron, we drew the interest of the CERN Management to the design of an ion synchrotron optimised for such a medical application. This became PIMMS, the Proton Ion Medical Machine Study, on which physicists and engineers from CERN, TERA and the MedAustron project worked for four years under the direction of Phil Bryant. In parallel, with TERA, I proposed that the Italian government finance a treatment centre based on an improved version of the PIMMS synchrotron, later called the PIMMS/TERA project. As the centre would cost more than 100 million euros, this was a hard sell, but the Italian government finally put up the money in 2001. In 2003, the CNAO Foundation, with its team of 26 physicists and engineers took over the project. Sandro Rossi, who had been the TERA Technical Director for almost ten years, became the CNAO Technical Director and, later, its Director-General. With the help of INFN, in autumn 2005, the construction of the Centre started in Pavia, an ancient university town close to Milan. In 2011, the first proton irradiation took place and, in 2012, exactly 20 years after the creation of TERA Foundation, the first patient was treated with a beam of carbon ions.

When the first patients were treated at CNAO, I felt that I'd done very interesting things in physics, but hadron therapy was the best thing I'd done in my professional life.

I am now President Emeritus of CNAO, and I have the satisfaction of seeing that the Centre is still growing. More than 5000 patients have been treated, 55% with carbon ions, and more and more patients are children: in 2023, 62 paediatric tumours were irradiated. Moreover, a proton gantry is being installed and a novel boron neutron capture therapy system will be operative in 2026. Overall, one can say that CNAO, as a spin-off of CERN and TERA, fully justifies my motto "Physics is beautiful and useful".

This video shows how technologies developed for particle accelerators, detectors and analysis have found their way into medical applications.

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This interview is adapted from the 2004 book "Infinitely CERN", published to celebrate CERN's 50th anniversary, and was updated with the help of Ugo Amaldi in 2024. Ugo was one of the speakers at the recent CERN70 public event "From particle physics to medicine ". A new PET digital learning module is available now for high-school students to help save a virtual patient, find out more via cern.ch/petlearningmodule.

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