The outlook for children with cancer grows more promising every day. According to the American Cancer Society, about 80% of kids with cancer are surviving at least five years past their diagnoses. Advanced radiation therapy like proton therapy is increasing that positive trend.
Like other forms of radiation, proton therapy uses a beam of high energy directed at a tumor to kill its cells. Proton therapy offers some unique benefits, especially for pediatric patients with developing organs more sensitive to radiation exposure.
Leaving more of the body untouched by radiation is especially important when treating cancer in children, whose bodies are still growing. Although radiation is an extremely effective tool to kill cancer cells, too much can harm healthy tissue and increase the risk of new cancer.
The high precision of proton therapy protects more healthy tissue than regular, x-ray-based radiation methods. Proton therapy can be used for children of all ages, but the benefit is greatest for very young children and infants.
Reducing the Risk of Future Cancers
Because children’s bodies are still growing and developing, pediatric tumors—especially those near the brain, head, neck, spinal cord, heart and lungs—are particularly challenging to treat with conventional radiation, which can be associated with significant toxicities.
Proton therapy largely prevents these sensitive areas from receiving any measurable dose of excess radiation. The result is fewer side effects during treatment and fewer long-term side effects than seen from conventional radiation including developmental abnormalities, growth delay, reduction in IQ and intelligence, and secondary cancers.
Childhood cancers treated with proton therapy therapy include:
- Medulloblastoma
- Low and high grade gliomas
- Ependymoma
- Germ cell tumors
- Craniopharyngioma
- Atypical teratoid rhabdoid tumors (AT/RTs)
- Other rare brain tumors
- Rhabdomyosarcoma
- Ewing sarcoma
- Other types of sarcomas
- Neuroblastoma
- Retinoblastoma
- Lymphoma, including Hodgkin lymphoma
Reducing Excessive Radiation
Proton therapy is most useful when a tumor is in or near a sensitive area of the body. Brain tumors are an example.
“If a child has a tumor located on one side of the brain, protons can effectively eliminate any radiation from traveling to the other side of the brain,” notes Matthew Ladra, M.D.,M.P.H., director of pediatric radiation oncology at the Johns Hopkins Kimmel Cancer Center at Sibley Memorial Hospital. “Excess radiation to developing brains has a chance of causing difficulty with learning and memory later in life, so anything that gets rid of the ‘spillover’ dose is great for our kids. Spinal tumors just behind the heart, tumors next to the eye or tumors in the muscles next to reproductive organs are all situations where proton therapy shines and can reduce the chance of having any negative impact on those organs.”
Minimizing the ‘Exit Dose’
Conventional radiation treatment uses a beam of energy that can pass through the human body. When directed at a tumor, the beam goes through the tumor and some of that radiation travels out the other side. That extra radiation, called the “exit dose,” can affect healthy tissue as it leaves the tumor.
Proton therapy, in contrast, can be adjusted to stop at the edge of the tumor, with very little exit dose.
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