Stefan Both

Proton professor fights cancer

The University Medical Centre Groningen (UMCG) is starting a new type of radiation therapy for cancer patients next month: proton therapy. Stefan Both, the very first ‘proton therapy professor’ in the Netherlands, symbolises the collaboration between physics and medical science.
By Freek Schueler / Photo by Reyer Boxem / Translation by Sarah van Steenderen

Both works at the radiotherapy department at the UMCG. Here, one of the very first proton therapy centers in the Netherlands is being constructed. Both hides his friendly eyes behind designer glasses. However, he looks as though he is still getting used to everything. And he is. He moved to the Netherlands for his new position only two months ago. What are his first impressions? ‘There are regulations for everything.’

He is originally Romanian, but he describes himself as ‘pretty global’. After he finished his physics studies, he moved to the United States to become a medical physics consultant, then later he moved on to the University of Pennsylvania, in Philadelphia. He started working as a professor at the RUG two months ago.

‘I was nicely surprised to find all the great work which has been done here, and I identify very closely with the goals and vision of this department.’ He will be working on the further development of the proton therapy in Groningen.

Proton therapy?

Cancer treatment can be divided into three categories: surgery, chemotherapy, and radiotherapy. In the case of the latter, conventionally, powerful X-rays would be used. This type of radiation affects the cancer cells’ DNA, killing them. Unfortunately, the radiation doesn’t just affect cancer cells. In addition to the tumour, healthy tissue is damaged as well.

The novel proton therapy doesn’t fire electromagnetic radiation at the tumour, but protons: particles from the atomic core. ‘And protons are unique! Protons release most of their energy at the end of their trajectory.’

This means it’s possible to treat tumours with great accuracy. Think of it as a minuscule bullet that stops moving halfway through the body: all the other tissue stays intact.

Any tissue that the protons do touch before arriving at the tumour is in general less affected in comparison to conventional radiotherapy. This is especially important when it comes to treating children. Because the healthy surrounding tissues in children are still growing, proton therapy can work especially well for them.


The idea behind proton therapy is not new. The potential advantages to protons were already identified fifty years ago. But the technology to make it work has evolved tremendously over the past few decades. The UMCG will be using a technology called ‘pencil beam scanning’. This enables radiation oncology physicians to treat the exact shape of the tumour in 3D, using a radiation pencil. This ensures that only the cancerous tissue is radiated.

This is an amazing development, of course. But this kind of precision is also one of the new technique’s pitfalls. Simply put, a relatively small change in circumstances may lead to large deviations. This could be a different patient, a different organ within the same patient, or the way the machines are calibrated. Organs that move, such as the lungs, are also more difficult to treat because the therapy is so precise.

The challenge lies in deploying the therapy to ensure that it can be used advantageously and accurately on every single body part and every single patient. But we’re not there yet.


That’s partially due to the current high costs of the treatment. The machines needed are usually several storeys high. In the machine, there is a couch, which holds the patient, and a snout, which emits the radiation. At the UMCG, the couch doesn’t just move horizontally and vertically; it’s robotic and it can turn and tilt to allow the machine to radiate patients from all angles.

Both’s role

Both is not a physician. ‘My role remains within the boundaries of my profession’, he says. His focus lies on the technological advances in radiotherapy, and partners with physicians to introduce them safely to the clinic, while he remains engaged to push the envelope to deliver the best possible treatment to patients.

One example is adaptive radiation therapy: in this type of therapy, the radiation can be adjusted to fit the situation and size of the tumour on a daily basis. Together with colleagues working on the issue of how to radiate moving organs, he develops tools and instruments to be implemented in the clinic and advises doctors on how to best use them.

Medical physicists help doctors to treat patients the way they aim to. Both: ‘It’s not always that what you see on the computer, it is also happening in the patient. We are bridging the gap between the maturity of the technology and the clinical requirements.’

Both’s biggest goal is to make optimal use of the proton’s characteristics. This will certainly keep him busy for the time being. And all those regulations? ‘There are pluses and minuses to that, but overall I think it has pluses’, says Both.


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