What proton therapy is, in plain language
Proton therapy is a type of radiation treatment for cancer. Like standard radiation, it aims to damage cancer cells so they cannot grow. What differs is the kind of beam it uses and how that beam stops inside the body.
What this page covers
- How proton therapy works.
- How it differs from the standard radiation used in Canada.
- What the evidence says.
How does proton therapy work?
Standard radiation uses X-rays, also called photons. A photon beam passes through the body from front to back. It gives part of its radiation to the target and part to the healthy tissue in front of and behind it.
Proton therapy uses protons instead. A proton beam releases most of its energy at a set depth and then stops. That stopping point is called the Bragg peak. Because the beam stops, little or no dose goes beyond the target.
In practice, this can mean less radiation reaching nearby healthy tissue. Whether that difference matters for a particular person depends on where the cancer is and what sits beside it. That is a judgment for a radiation oncologist.
What does the evidence say?
Proton therapy helps most when the cancer sits near tissue that is hard to protect with standard radiation. The uses with the strongest expert consensus are: skull-base tumours, brain and spinal-cord tumours, some eye tumours, childhood solid tumours treated with curative intent, and some re-irradiation where the total dose to a critical structure would otherwise be too high.
In these established uses, the goal is to reduce side effects without weakening the treatment, and studies support that disease control remains comparable to standard radiation. In children, lowering the dose to healthy, developing tissue matters for long-term health; studies in children show tumour control as good as standard radiation, with some long-term side effects, such as hearing loss or hormonal problems, seen less often. Publicly funded pathways for children’s proton therapy exist in Canada and are used; families should pursue them first through their child’s oncology team.
Prostate cancer is an important example of a different kind. Proton therapy is used for prostate cancer and targets the tumour with high precision. Because a proton beam delivers no dose beyond its target and a lower dose on entry, less radiation reaches the healthy tissue around the prostate than with standard radiation. This can lower the risk of side effects such as impotence, incontinence, and bowel problems. Centres offering proton therapy report high rates of tumour control for prostate cancer. How public programs cover it varies by province; talk with your oncologist about the best option for you.
What proton therapy means for your cancer is a question for your oncologist. Who this treatment is for, and how the decision is made, is explained on its own page: who proton therapy is for.
Frequently asked questions
Is proton therapy experimental?
Proton therapy itself is an established treatment in use for decades. For some uses the evidence is strong; others are still being studied. Whether a given use counts as standard or research depends on the diagnosis.
Does proton therapy hurt?
The treatment beam itself is not felt during delivery. Side effects depend on the area treated and are discussed by the treatment team.
How long does proton therapy take?
Treatment is usually given on weekdays as an outpatient. The number of sessions depends on the diagnosis, and the full course can run from a few weeks to a few months. The treating centre sets the exact plan.
Is proton therapy covered in Canada?
Provinces and territories have out-of-country funding routes for treatment not available in Canada, and these routes are used for proton therapy. The rules depend on where you live. See check funding in your province.
Sources for this page (6)
- How proton therapy works and the Bragg peak; uses with expert support: Ontario Health, Health Technology Assessment, “Proton Beam Therapy for Cancer,” Ont Health Technol Assess Ser 2021;21(1):1-142. pmc.ncbi.nlm.nih.gov (checked 2026-07-06)
- Uses with the strongest expert consensus, including skull-base, brain and spinal cord, eye, and childhood tumours: American Society for Radiation Oncology (ASTRO), Proton Beam Therapy Model Policy. astro.org (checked 2026-07-06)
- Publicly funded pathways for children’s proton therapy exist in Canada and are used: Tsang et al., Proton Therapy in Canada, Int J Radiat Oncol Biol Phys (Red Journal), 2022, S0360-3016(22)03642-2. redjournal.org (checked 2026-07-06)
- Proton therapy for prostate cancer, precision, and sparing surrounding tissue: Miami Cancer Institute (Baptist Health South Florida), proton therapy. baptisthealth.net (checked 2026-07-15)
- Proton therapy for prostate cancer, lower risk of impotence, incontinence, and bowel problems, and reported tumour control: University of Florida Health Proton Therapy Institute, prostate cancer. floridaproton.org (checked 2026-07-15)
- A proton course is given on weekdays as an outpatient, with the number of treatment days depending on the diagnosis: Proton Therapy Center Prague, FAQs (course of 5, 19, or 21 working days, Monday to Friday). ptc.cz (checked 2026-07-15)
Every statement on this page is drawn from the sources listed below. Last updated: 15 July 2026.
This page is for general education only. It is not medical advice and it is not a decision about your care or your funding. Only your treating physician can advise you on treatment. Only your provincial or territorial health plan can decide whether it will fund treatment outside the country. protontherapy.ca is an information resource by Maple Med Global (MMG Medical Tourism Inc.), Toronto, Canada. We are not a hospital, a clinic, or a government body, and we do not provide medical care.