Protecting what matters most: Proton therapy for brain and central nervous system tumors

Brain and central nervous system (CNS) tumors exist in a wide range of types, from aggressive to slow growing. Approximately two-thirds of the tumors that grow in the brain aren’t cancerous at all, but they still might cause harm.

Brain and CNS cancers can affect people of all ages and can arise spontaneously without any reason or risk factors. These tumors affect quality of life and how patients function day to day; depending on their location, they can cause physical weakness or impact cognitive function, forcing patients to adjust to new and potentially long-term challenges.

Radiation oncologist Lisa Ni, MD, treats children with all types of cancer as well as adults with brain, ocular and CNS cancers at Fred Hutch Cancer Center – Proton Therapy.

Some brain cancers are especially suitable for treatment with protons.

When it comes to adults, these cancers include:

Chondroma and chondrosarcoma: These tumors are slow-growing and resistant to radiation. Proton therapy allows physicians to deliver a higher dose to increase the likelihood of killing the tumor.
Glioma and meningioma: Certain types of gliomas and meningiomas often grow near critical structures or parts of the brain that control thinking, memory, movement and speech. Proton therapy can deliver focused radiation to the tumors while sparing those critical structures and normal brain tissue.

When it comes to children, these cancers include:

Medulloblastoma: Proton therapy is particularly beneficial in treating these tumors because it can effectively deliver radiation to the entire brain and spine, while significantly reducing radiation exposure to developing organs like the heart, lungs and digestive system, which is especially important in children and young adults.
Ependymoma (brain and spine): Proton therapy may be useful in treating these tumors, as they can occur near vital structures in the brain and spinal cord, allowing higher doses to be used to control the tumors while limiting long-term side effects from radiation.
Germ cell tumors: These tumors arise from reproductive cells and although they often occur in reproductive organs, they can also occur in the brain (and other parts of the body). Proton therapy allows providers to precisely deliver radiation to the tumor and areas at high risk for recurrence, while limiting radiation dose to the healthy developing brain, including areas that are important for memory.

“When deciding on the best treatment plan for my patients, I always consider several factors, such as the location of the tumor and how close it is to critical organs such as the brainstem or eyes,” she said. “With protons, we can increase the dose to the tumor while avoiding radiation to surrounding healthy tissue. All patients benefit from reduced radiation to healthy tissue, but especially young, otherwise healthy patients or those with slow-growing tumors. Avoiding the healthy tissue can reduce the risk of long-term side effects and secondary cancers caused by radiation.”

Ni highlighted two cases when she considered proton therapy the superior treatment modality, one involving a young girl with medulloblastoma, a fast-growing, relatively rare type of brain cancer, who needed radiation to her brain and spine.

“Because we have to treat such a large area, proton therapy allowed us to better limit dose to the heart, lungs, kidneys and bowel,” Ni said. “She also needed a proton boost to the tumor bed — the area where the tumor was before surgery — in the back of the head. In this case, I expect that using proton therapy will reduce her long-term risk of side effects and risk of secondary cancers down the line.”

She also recalled a man she treated a year ago with chondrosarcoma, which was growing at the base of his skull. The surgeon was able to remove most of the tumor, but some residual tumor remained close to the brainstem.

“Chondrosarcomas are resistant to radiation, which meant we had to treat him with a high dose,” Ni said. “Using protons allowed us to do that while sparing as much dose as possible to the brainstem, which controls critical functions such as balance, breathing, heart rate and reflexes. He is doing very well now, a year out from treatment.”

The CNS specialists at the proton therapy facility treat an average of 110 CNS patients a year, more than half of whom are brain tumor patients. A little fewer than half are children. Along with Ni, those specialists include Ralph Ermoian, MD, Lia Halasz, MD, Simon Lo, MB, FASTRO, Yolanda Tseng, MD and Sara Hardy, MD, MSci.

This level of experience is a key advantage for those receiving treatment at Fred Hutch – Proton Therapy, Ni said. Fred Hutch oncologists collaborate on their cases and stay up to date with the latest research and indications for proton therapy and other types of radiation treatments. Patients can rely on leading-edge, evidence-based recommendations, and staff is experienced in helping patients of all ages and backgrounds.

“Being diagnosed with a brain tumor is scary,” Ni said. “We try to make their care here as predictable and comfortable as possible.”

As a National Cancer Institute-designated comprehensive cancer center, Fred Hutch regularly conducts clinical research and is currently enrolling patients in a clinical trial studying proton therapy for leptomeningeal disease (LMD). LMD is metastatic cancer in the cerebral spinal fluid surrounding the brain and spinal cord.

To treat LMD, physicians must irradiate a large area including both the brain and the spine. The study is investigating whether protons are better at avoiding radiation to the hippocampus, the part of the brain responsible for memory and learning. Sparing radiation to the area may improve cognitive outcomes.

As one of the investigators on the LMD study, Ni said she is interested in researching how to use proton therapy to effectively treat tumors while decreasing side effects, motivated by the wide range of patients that she treats.

Learn more about proton therapy for CNS cancers.