What is Proton Therapy
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Protons for Brain Cancers

Protons for Brain Cancers

Nearly 80,000 Americans are diagnosed each year with a primary brain tumor, 4,600 of whom are children. Brain tumors are abnormal cells in the brain, and primary brain tumors originate there, rather than having spread from another part of the body, which are called metastatic cancers. There are numerous types of brain and central nervous system tumors, many of which can be treated with a combination of therapies. Surgery to remove the bulk of the tumor is often the first step. Since microscopic disease is often left or tumors are not suitable for surgery, proton therapy can be an important treatment.

Our brain and central nervous system tumors expert, Dr. Lia Halasz, explains: "The best candidates for proton therapy have brain tumors that are in higher risk locations, or where long-term side effects are important, among others."

Proton therapy is also recommended for the treatment of tumors that are irregularly shaped, located near critical organs and brain tissue, or when patients have previously received radiation therapy to the area.

Because the brain is so complex, treatment in this area might have long-term implications for the nervous system or other organs. The goal of proton therapy for brain tumors is less radiation exposure to healthy brain tissue, brainstem, cochleae, eyes, optic nerves, and pituitary gland. This is because doctors can precisely target protons, which are particles, to stop at the tumor and not continue beyond it. Also, the maximum dose is released right at the tumor rather than before it, the way radiation waves (photons) do.

In the image above, you can see how protons can more precisely target the tumor and spare surrounding healthy tissue from radiation exposure.

"Most of my patients are concerned with how radiation therapy is going to affect their neurocognitive abilities (such as multi-tasking and short term memory) in the long term," says Dr. Halasz. "Proton therapy can decrease the excess dose to normal brain tissue, reducing the risk of negative long-term neurocognitive outcomes. This recent paper on neurocognitive outcomes after proton therapy versus photon therapy for pediatric brain tumor patients is interesting," says Dr. Halasz. The study found that proton therapy is associated with favorable outcomes for intelligence and processing speed, and further reduce neuropsychological morbidity of brain tumor treatment.

"These are difficult studies to perform because they require long-term follow up with multiple intensive evaluations. We currently have an open randomized trial (BN-005) that asks this question for our adult patients with low-grade glioma."

Clinical trials are the tool physicians use to determine if a treatment works, is better than another treatment, or answers a fundamental question. Many proton therapy-related trials evaluate the difference between proton and photon treatment outcomes in patients. Many show that protons are superior in terms of reduction in long-term side effects and related hospitalizations. Sometimes clinical trials cannot be randomized, as when they involve children, which makes the results more open to scrutiny. Despite this, evidence is growing that proton therapy has better outcomes for many brain cancer patients, including children.

Because brain tumors vary so much, your treatment plan can depend on a wide range of factors, from the tumor's type, size, and location to your age and overall health. Only your doctor can tell you the best treatment plan for you, but ask about proton therapy as an option. Though its use is rapidly expanding throughout the world, proton therapy is still a relatively new option in our region, as the Center is the only proton therapy facility in the Pacific Northwest.