Proton Beam Therapy Pioneer Improves Survival Rates for Children with Cancer

Jan 11, 2016 at 05:35 pm by admin

Last month, a few weeks before Christmas, St. Jude Children’s Research Hospital presented us with another world-class “first”— the St. Jude Red Frog Events Proton Therapy Center –the first center of its kind dedicated exclusively to pediatric cancer treatment.

But for Thomas Merchant, DO, PhD, and Chair of Radiation Oncology at St. Jude, it was a personal milestone, as well.  Even before choosing a career in medicine, as a senior studying nuclear engineering at the University of Michigan, Merchant wrote a paper on particle therapy research being done at the Swiss Institute for Nuclear Research in Villigen, Switzerland (now known as the Paul Scherrer Institute). Twenty-five years later, as a St. Jude researcher, he visited the institute and studied firsthand its program in proton spot scanning.

There, in perhaps the premier facility in the world where proton spot scanning, aka pencil-beam scanning, was developed, he experienced what many inventors, scientists, and researchers identify as an “Aha!” moment.

“We have GOT to have this!” Merchant realized.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              “St. Jude had proton therapy on its radar and followed it very carefully,” he explained. “But the technology available then (in 2008) wasn’t this leading edge technology.  When it became available, that’s when we made the decision to develop our own treatment center.”

Now that St Jude has treated its first few patients, carefully selected, in meticulously controlled clinical trials, he marvels at the ‘unbelievable’ focus and accuracy in delivering a radiation dose precisely shaped to match its target.

Previously available pencil-beam systems were limited by their comparatively large beams. “Our beam size is the smallest clinical beam in the United States today,” he believes.

Being one of the first systems to employ exclusively pencil-beam technology is not without risks.  Whether to include, in part, older “passive scattering” technology with the new was a big decision, said Merchant. “Since we had waited for this new technology to implement proton therapy however, we chose to make the entire facility pencil-beam. Obviously that was a good decision.”

Medical technology is perpetually threatened by obsolescence, so one of Merchant’s concerns was how long the new technology would retain its cutting edge.  “This is one of the biggest challenges that the administration put before me in 2011,” he recalls. “They said, ‘You need to open a proton therapy center in the next five years, and it absolutely has to be cutting edge.’ But how do you predict the future?”

Hitachi Ltd.’s ability to make improvements during system development—even up to the last minute—made them an attractive proton therapy vendor partner, said Merchant. “The Center was designed so that we can make modifications over time that will also keep it cutting edge for a long time. What we have today is just the beginning; a year or two from now, it will have more functionality –and allow us to do more and more.”

In the future, will all children be treated with proton therapy?

“I think it’s moving in that direction. The number of children each year in the United States who need radiation therapy as part of their front-line management is difficult to estimate, but may be from 3,000 to 5,000. If I had my way, we would treat every child with cancer here –but that’s not practical. So St. Jude helps others by performing trials that are designed to treat a specific number of patients, and we share those results with other institutions in the U.S. and around the world.”

Merchant is not a stranger to successful research results that have far-reaching benefits. His proudest achievement, in fact, is a change in U.S. and international philosophy regarding the use of radiation therapy on brain tumors in young children under the age of three—which has saved countless lives. 

“When I came to St. Jude (from Memorial Sloan-Kettering Cancer Center, New York) in 1996, it was to implement conformal radiation therapy using X-rays.  At that time, children under the age of three with brain tumors did not receive radiation therapy as a part of their initial treatment because everyone was concerned about the side effects of radiation.”

Then, for example, children with a tumor known as ependymoma would have surgery and chemotherapy, receiving radiation therapy (potentially) only when the tumor grew back. Merchant characterizes those results as “miserable”, with five-year overall survivals in the 40% range. His efforts galvanized St. Jude’s teams to offer these children radiation immediately after surgery. Five-year overall survival rates have since jumped to 85%.

Merchant then led a five-year national trial (2003-2007) that duplicated St. Jude’s results.  “Just by bringing radiation therapy in immediately after surgery for those very young children, we doubled their survival. I’m proud that we pioneered the use of radiation therapy in children under the age of three years with brain tumors.”

He points to St. Jude’s track record of doing pilot studies that lead to national and international studies that bring about change.  “We’re going to do the same with proton therapy,” he predicts.

Seeing children in follow up for tumor surveillance once treatment is completed is the most challenging part of his work, he notes.  “We’re concerned about each and every patient. We want clean scans, good exams, and we worry a lot about that.”

Does working with children make the job emotionally more difficult?

“Heartbreaking things happen here all the time; but by and large it’s a joyous place to work.  Our results are good, and that keeps us going.

Post-college, Merchant worked for the French Atomic Energy Commission (CEA), evaluating radiation protection and safety and partnering with investigators at the famed Curie Institute. After medical school (Chicago College of Osteopathic Medicine), he was a Fulbright Scholar to the Netherlands at the University of Utrecht, where he received his PhD, cum laude, in experimental pathology.

“The great thing about the field of pediatric oncology and radiation oncology,” he notes, “is the small community. We know each other; we really enjoy helping others – both nationally and internationally.” 

For Merchant, this particularly includes one person: his wife, Dr. Jenny Tibbs, who also practices radiation oncology in Memphis.

RELATED LINKS: (“What are the advantages of proton therapy?”)

Sections: Archives