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Proton therapy, the most advanced form of radiation treatment around today, does less damage to healthy tissue, allows doctors to target tumors more precisely, and results in fewer side effects. SteadyHealth spoke to a medical physicist to find out more.

Cancer is — undeniably and profoundly — scary. Over 38 percent of adults will be diagnosed with some type of cancer over the course of their lives, along with numerous children. Each year, around 14 million new cases are identified, and a shocking 9.6 million people lose their lives to cancer. Lung, colorectal, stomach, liver, and breast cancers are the most deadly.

For those personally affected by cancer, because they or someone they care about was diagnosed, it’s easy to lose hope. But though cancer is a leading cause of death worldwide, there’s also good news — with the right action, lots of cases can be prevented and many more cured. This World Cancer Day, the message is that progress is possible. A better future is within reach.

Proton therapy sits at the cutting edge of that better future. SteadyHealth got to talk to medical physicist Dr Charlotte Brouwer from the renowned University Medical Center Groningen's Proton Therapy Center in the Netherlands to find out more.

What is proton therapy?

Proton therapy is a relatively new method to deliver curative radiation to treat cancer. Like conventional radiation therapy (radiotherapy), which uses high-energy X-rays and gamma radiation, proton therapy uses protons (positively-charged subatomic particles) to damage, and eventually kill, cancer cells.

Although conventional radiotherapy is very successful in the treatment of cancer, the radiation beams used in the process can’t be controlled with great precision — so it damages surrounding healthy tissue right alongside cancer cells. Proton therapy, on the other hand, can be adjusted to “bombard” a specific target with a beam while leaving the surrounding healthy tissue relatively unscathed. This happens because protons have a larger mass than electrons, reducing scattering to a minimal level.

Using a particle accelerator, the machine first extracts and collects protons from hydrogen, which is transformed from its natural gas state to a plasma state. The large magnets then “collect” and accelerate those protons to nearly 70 percent of the speed of light so they can gain enough energy, and finally leave the accelerator in the form of a proton beam. The proton beams are then navigated to the "gantry" (a robotic chair where the patient receives treatment), and finally to the patient — or, more precisely, the cancer itself.

When the protons travel through the body, they lose energy, and therewith also speed. When the protons are slowed down to a specific degree, the energy they give to the surrounding molecules greatly increases and the protons stop moving. The time protons spend near the cancer cells is enough for the protons to give all of their remaining energy to the molecules that make up these cancer cells, including their DNA. This disrupts molecules' normal function, killing cancer cells.

The main types of proton therapy are:

  • Passively scattered proton therapy, where a narrow beam is scattered to a larger area, resulting in higher unwanted radiation doses.
  • Uniform scattering, which uses a broad beam to cover the treatment area.
  • Pencil beam scanning, which is extremely precise but demands longer treatments. This technique is so targeted that even breathing and bowel movements can send the beam outside the treatment area. Although relatively new, this type of scanning has the greatest potential in the future of proton therapy.

What are the main benefits of proton therapy?

The fact that children are especially vulnerable to the effects of radiation, since they’re still growing, makes proton therapy uniquely suitable for the treatment of many pediatric cancers. Proton therapy can also make a big difference where tumors have taken hold in parts of the body that contain important and sensitive organs — breast cancer treatment may, for instance, require radiation to be delivered close to the heart. 

The precision of the radiation greatly reduces the risk of secondary cancer as a result of the initial treatment, and research has shown proton therapy to have fewer, less intense, and less long-lasting side effects than conventional radiotherapy, so patients generally tolerate proton therapy very well.

Even with this innovative technology, going through cancer treatment won’t be easy — but patients who have been deemed suitable candidates for proton therapy can take comfort in knowing that they’re receiving the best care science has to offer, from a dedicated medical team who will work hard to meet their needs. “It is really exciting to be involved in all technological and clinical developments,” Dr Brouwer told SteadyHealth

What kinds of cancers can be treated with proton therapy?

Proton therapy can currently be used to treat many localized solid tumors that haven't metastasized, and the UMC Groningen highlights breast cancer, cancers of the neck and head, and brain tumors as cancers that are often better treated using this method. Not everyone benefits from proton therapy, and patients who have access to a proton therapy center will have to ask their treating medical teams whether they would make good candidates.

If proton therapy is so awesome, why can’t everyone have it? 

Proton therapy can be up twice as expensive as X-ray radiation. The treatment is complex and still not widely available — in the United States, for instance, only 29 regional centers are currently able to offer the treatment, and the situation is similar in most of the rest of the world. Dr Brouwer also adds that not every proton therapy center is the same — “high quality photon therapy can be better than proton therapy in older treatment centers.”

In the Netherlands, Dr Brouwer says, everyone who benefits from proton therapy “can be treated in Groningen for the moment”, at the Proton Therapy Center that opened its doors in 2018.

Before choosing the best course of action, both photon and proton radiation treatment plans will be designed for each patient, after which their medical team chooses the option that is most suitable for the individual. “In Holland we follow the ‘model-based approach’,” Dr Brouwer shares, “and compare photon and proton plans on Normal tissue complication probability (NTCP).”

Patients diagnosed with brain cancer, chondrosarcoma (a type of bone cancer), and pediatric patients are the most obvious candidates for proton therapy, she explains. 

What can patients expect from proton therapy?

At UMC Groningen’s Proton Therapy Center, patients will meet with their radiation-oncologists before they start their treatment. This gives the medical team the chance to make sure they have all the information they need about the patient’s medical history and personal needs, and that the patient knows what they can expect. They’ll learn about the number of sessions they need, for instance, and what side effects are common. Patients receiving proton therapy for cancers of the head and neck may experience fatigue, a dry mouth, and difficulty swallowing, for instance. The skin around the treated area is also likely to become red and itchy.

Patients in Groningen are connected with a “patient service”, a dedicated team of people who help those receiving cancer treatment navigate the process, answering their questions every step of the way. 

After that, imaging techniques are used to pinpoint the exact region that will be treated, and where necessary, a mask will be made to keep the patient in the proper position during the radiation sessions. 

Once the treatment plan is complete, patients are ready to start their proton therapy sessions. Their exact number varies from case to case — patients might have anywhere between five and 39 treatment sessions — and individual treatments can last from 15 to 45 minutes. The radiation itself may take no longer than five minutes, and many patients report that it’s hardest for them to stay perfectly still the entire time, surrounded by uncomfortable noises. Patients are monitored throughout the treatment, which is itself painless, and are able to continue with their day after a session. 

How will proton therapy change in the future?

Dr Brouwer shares that UMC Groningen’s Proton Therapy Center “expects to publish the first results on head and neck cancer in the coming years”. Over the next decade, she says, “we will learn more on which patients and organs will benefit from proton therapy”. 

In future, the treatment may become even better: “I expect less bowel toxicity for pelvis patients. And less fatigue in general.”

Progress isn’t just possible, but already underway. A better future is indeed within reach.

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