According to a 2017 Penn and CHOP study, proton therapy lowers treatment side effects in pediatric head and neck cancer patients. Treatment appears to be just as effective as traditional photon radiation while improving quality of life both during treatment and for years after for these young patients. MedicalExpo e-magazine spoke with the study’s senior author Christine Hill-Kayser, MD, chief of the Pediatric Radiation Oncology Service at Penn Medicine and an attending physician at the Children’s Hospital of Philadelphia (CHOP).
ME e-mag: Do pediatric cancers pose different challenges than adult cancers?
Christine Hill-Kayser: Absolutely. Firstly, because the cancers that children get are, for the most part, very different in the way they behave biologically. Also, taking care of pediatric patients is very different. With a child, you’re really taking care of their whole family. A lot of conversations are with parents who need to make extremely difficult decisions. The third difference is that children have unique medical needs. Many children, for example, in order to have radiation need anesthesia so we have an anesthesia team with whom we work very closely.
“Proton therapy is very effective at treating most pediatric cancers as we can reduce the amount of normal tissue exposure.”
ME e-mag: How is proton therapy effective for treating pediatric cancers?
Christine Hill-Kayser: The central benefit is that it spares normal tissue. When x-rays, the more standard type of radiation therapy, enter a patient’s body, we can’t make them stop and so as they trail off, they deliver a radiation dose beyond the location of the tumor. Protons, because they are heavier and have a positive charge, don’t do that. They enter the patient’s body and, using complex hardware and software, we can decide exactly where we want them to stop.
So, for example, if you are treating a patient’s spinal cord, you can use a proton beam that enters from the patient’s back and stops right in front of the area you want to treat. If you were to use x-rays that can’t stop, you expose all the tissues in front of the spinal cord—heart, lung, bowels, organs of fertility—to radiation. For children, whose organs are especially vulnerable to radiation damage and who are expected to live a long time, the normal tissue sparing is a significant benefit.
ME e-mag: Is proton therapy better at treating certain types of cancers?
Christine Hill-Kayser: Certainly, there are many parts of the body where proton therapy is beneficial. For example, with a brain tumor, you want to leave a large part of the brain unexposed to the radiation. But there are also situations that don’t require proton therapy. For example, some patients with leukemia need radiation of their entire brain. Because the treatment goal involves the whole brain, there is no benefit to choosing proton therapy.
See pictures of CHOP waiting room:
ME e-mag: Can it be combined with chemotherapy or surgery?
“Protons enter the patient’s body and, using complex hardware and software, we can decide exactly where we want them to stop.”
Christine Hill-Kayser: Absolutely. Almost all pediatric cancer patients require chemotherapy, which is a systemic therapy that travels throughout the patient’s body. For some patients, for example those with Hodgkin Lymphoma, chemotherapy will be given, patients will have a break, and then they go on to radiotherapy. For other patients, chemotherapy and radiotherapy must be given at the same time. Surgery is, like radiation, a local treatment. We can do either radiation or surgery, or a combination of the two.
ME e-mag: What is the research saying about its effectiveness?
Christine Hill-Kayser: From the constant research effort being undergone at our center and others, the findings have been overwhelmingly positive. We think that proton therapy is very effective at treating most pediatric cancers, with potential to improve survivorship, as we can reduce the amount of normal tissue exposure.
ME e-mag: What future innovations can we hope to see?
Christine Hill-Kayser: Now that we have shown it is safe and effective, the next question is how to use proton therapy to do new things. For example, we have a study on how to use proton therapy to treat kidney tumors in children in a way that involves targeting the retroperitoneal area rather than a larger part of the abdomen. Another novel question is, now that we can reduce normal tissue exposure through proton therapy, can we add more aggressive systemic therapies in a way that patients can tolerate, and would this lead to better outcomes?
ME e-mag: Are you hopeful that pediatric cancers can be fully cured long term?
Christine Hill-Kayser: I am absolutely hopeful. We have made a ton of progress over the past 40 to 50 years but there is still a lot of progress to be made.
ME e-mag: On a personal note, why did you decide to specialize in pediatric cancers?
Christine Hill-Kayser: I developed a longstanding passion for taking care of pediatric oncology patients while volunteering in hospitals as a college student. I stumbled upon radiation oncology in medical school and came to really love its unique blend of patient care and intellectual thought—thinking about how space, math, and physics relate to patient care.
ME e-mag: How many staff and patients are at the Pediatric Proton Therapy Center?
Christine Hill-Kayser: We have three attending physicians. We usually are treating between twenty and thirty patients per day. The children come for daily treatments for anywhere from one to seven weeks.