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Johns Hopkins Pediatric

Proton Therapy FAQs for CNS Cancer



The outlook for many patients diagnosed with central nervous system cancers has improved in recent years. Through genetic sequencing and other technologies, researchers have found ways to better characterize tumors and tailor treatments to the unique tumor signature as well as the overall health of each patient. No longer are there one size fits all treatment solutions. Your treatment team will discuss with you care strategies that might include surgery, chemotherapy, immunotherapy, targeted therapies, and radiation and radiosurgery. 

Why Proton Therapy?

Proton therapy is a type of advanced radiation treatment. It takes advantage of a remarkable and unique characteristic of high energy particle beams and how they deposit ionizing radiation as they move through the body. Unlike conventional gamma or X-ray beams, which do not stop as they pass through the body, the depth of proton therapy beams can be controlled. As the charged particles come to a stop, all of their energy is deposited within the tumor with little to no exit dose to the surrounding tissues.

Because preserving healthy brain and spinal cord tissue is key to preserving neurological function, precise delivery of radiation is exceptionally important. This is where the precision of proton therapy comes into play. With conventional radiation, the powerful doses required to kill tumor cells can also damage significant portions of healthy tissue. Avoiding radiation to healthy central nervous system tissue and surrounding structures reduces the risk of treatment related side effects, including:

  •       Paralysis and other mobility issues
  •       Incontinence
  •       Vision loss
  •       Cognitive problems
  •       Memory loss

With image guidance and pencil beam scanning technology, proton therapy treatment at the Johns Hopkins Proton Center is amongst the most advanced in the world. Pencil beam technology allows for “dose painting” with a precise proton beam only a few millimeters wide to target the unique shape of individual tumors.

Treatment for Central Nervous System Cancers

When cancer and benign tumors infiltrate the brain or spinal cord, the consequences of treatment can often be as dire as the diagnosis. The Johns Hopkins Proton Therapy Center has the advanced technology and clinical expertise that central nervous system cancer patients need to exactly delineate and target tumors, reducing the range of uncertainty and optimizing tumor control.  

The patients most likely to benefit from this more precise treatment are those with tumors classified as low grade because they are slow growing and limited to a specific area of the brain or spinal cord. These characteristics also distinguish low-grade tumors from their highly malignant and aggressive counterpart that reach throughout the brain or other central nervous system structures. Whether the precision of the proton beam will benefit patients with these types of brain tumors is more uncertain and will require extensive research studies. 

Low-grade tumors, such as meningioma (a benign tumor that forms on membranes that cover the brain and spinal cord just inside the skull) and pilocytic astrocytoma (a slow-growing type of glioma brain tumor that originates from star-shaped cells called astrocytes) are examples of tumors more confined to a specific area of the central nervous system. 

The ability of the proton beam to stop at the tumor makes it the preferable option for patients with tumors that sit on or close to the spine or near other critical structures that need to be shielded from radiation, such as the optic nerve or spinal cord. Proton therapy may also be the best option to preserve fertility in women of childbearing age who have tumors near the pituitary gland or ovaries. Proton therapy’s toxicity-limiting precision also provides flexibility to increase doses. With other types of radiation treatment, doctors may decrease the radiation dose to the tumor to protect a vital structure nearby. 

Many factors are taken into consideration when discussing central nervous system cancer treatment with proton therapy. These include:

  •       Tumor type
  •       Tumor location
  •       Patient’s condition and prior treatments
  •       Systemic therapy options and plans
  •       Prior radiation therapy

Examples of central nervous system cancers where proton therapy is an option:

  •       Ependymoma
  •       Chordoma
  •       Low grade glioma
  •       Meningioma
  •       Pituitary adenoma
  •       Craniopharyngioma
  •       Re-irradition

Stereotactic radiation for brain and spine metastases is an area of investigation but is not currently performed using proton therapy

Proton Therapy CNS Cancer Experts: 

Victoria Croog, MD
Lawrence Kleinberg, MD
Brandi Page, MD
Kristin Redmond, MD, MPH

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