Proton therapy, the cancer treatment that can prevent lifelong side effects

A technician looks at a CT scan of the head of a patient lying on a stretcher in another room. Inside the skull, a large, perfectly outlined area can be seen. It is a tumor. The treatment begins. Within a few seconds, the malignant lesion is rendered in three dimensions on another screen. Just over a minute later, the procedure is complete, and the patient walks out of the treatment room unaided.

The three-dimensional image of the tumor was created using protons — subatomic particles accelerated to nearly the speed of light — offering one of the most innovative and exclusive treatments for certain cancers. Unlike conventional X-ray radiation, which uses photons, proton therapy is more precise and causes much less damage to healthy tissue. This precision is particularly crucial when there is a risk of affecting vital organs.

In just a few years, Spain has made rapid strides in adopting proton therapy. From having no facilities, the country is now completing 11 units within its public health system, with two already operational in the private sector. One of these is located at the Madrid headquarters of the Clínica Universidad de Navarra (CUN), where this newspaper had the opportunity to observe the technology in action.

Dr. Curtiland Deville, an American oncologist from Johns Hopkins University, has been using proton therapy to treat adults and children since 2010. According to the expert, this treatment “is indicated for patients who have undergone conventional radiation and have not been cured.” “It is also indicated when the cancer is in places that are difficult to access or operate on, such as the base of the skull or the sacrum [in the lower back], where you cannot apply such a high dose of conventional radiation,” he adds. “In our unit, we treat the most complex cases, and it is gratifying to offer patients something that wasn’t available to them before.”

The main advantage of proton therapy is its ability to prevent side effects that can diminish a person’s quality of life for years, decades, or even their entire life. “According to studies that have been carried out in hospitals in the United States that have been treating patients for many years, such as Saint Jude Children’s Hospital and MD Anderson,” explains Deville, “children treated with protons have advantages over those who receive conventional radiotherapy, such as better cognitive development, they do better at school and later at work. They live better thanks to having received proton therapy.” At the same time, the doctor notes, the anti-tumor effects of both treatments are comparable.

The major challenge with this new therapy is its cost. A single proton therapy unit, like the one at CUN, developed by the Japanese company Hitachi, costs around €40 million ($42 million). As a result, even in countries where proton therapy has been in use longer, there are still far fewer units than needed, leaving many patients unable to access the treatment, Deville admits.

In Spain, 10 proton therapy units are being installed in public hospitals across seven regions, thanks to a nearly €264 million ($276 million) donation from the Amancio Ortega Foundation. Another unit, also public, is under construction at the Marqués de Valdecilla Hospital in Cantabria.

Proton therapy machines are essentially particle accelerators. They require a new building the size of a tennis court, and the construction and commissioning process can take more than two years. The technology is based on hydrogen atoms, which consist of a proton and an electron. The protons are separated from the electrons and injected into a circular particle accelerator — a synchrotron — where they are compacted and accelerated to nearly the speed of light. From there, they pass into a second machine that can rotate 360 degrees, precisely delivering protons to the target area with the necessary intensity. Patients don’t see this massive machinery; instead, they lie on a robotic table inside a white gantry similar to those used for MRIs. A full session lasts about 35 minutes, although the radiation dose is delivered in just one minute; the rest of the time is spent positioning the patient correctly.

The arrival of proton therapy in Spain will not only pose a financial challenge but also a personnel one. To implement this technology, doctors, physicists, and specialized technicians must be trained at facilities where it is already in use, warns Javier Aristu, head of the CUN Unit. “Currently, we treat around 30 patients a day,” he explains. “In our unit, we have seven doctors, eight physicists, and we also require trained personnel, including nurses, assistants, and especially management technicians.” A third of the more than 1,000 patients treated at this hospital are children. Some of these patients are referred from public hospitals across Spain while waiting for the public units to start operating.

The argument in favor of this expensive therapy is that, in the medium to long term, it is cost-effective, as it reduces hospitalizations, additional interventions — such as the use of gastronomy tubes in head and neck cancer patients — and enhances the overall quality of life for patients, according to the doctors. Proton beams are far more precise than X-rays. They produce much less “explosive wave” damage and also allow for the tumor to be targeted layer by layer. “Ultimately, these beams sculpt the tumor in three dimensions,” says Felipe Calvo, scientific director of the CUN. While there is no concrete evidence yet that protons are more effective than photons in destroying tumor cells, Calvo believes they are. “[Protons] can fragment the DNA of tumor cells and prevent them from repairing themselves, something that can happen with conventional radiotherapy.”

The doctor highlights what is possibly the only affordable component of the entire system: the hydrogen cylinder. “With just 1.5 liters, we have enough protons for more than 20 years of operation,” he says.

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