Tour of the New Mercy Proton Therapy Center & How the Cyclotron Delivers Cancer-Killing Treatment

    By Kathleen Berger, Executive Producer for Science and Technology

     The massive size of a cyclotron is too big for a single floor of a building and too big to be delivered through doorways, so construction of additional building space at Mercy Hospital St. Louis was required. Before the new building had a ceiling and roof, a crane lifted the 30,000 pound cyclotron several stories into the air before lowering it into its new home at the David C. Pratt Cancer Center in July of 2021. A year later, the Mercy Proton Therapy Center is now open.

    Not only is cyclotron a cool name, but what it does as a particle accelerator is exciting too! Everything about the cyclotron and its new home in St. Louis, Missouri hinges on the proton found in the nucleus of the hydrogen atom, the simplest atom in nature.

    “The proton is the positively charged molecule. We can extract that proton from hydrogen gas to create this very steady beam which we use to target cancer,” said Robert C. Frazier, MD, Division Chief of Radiation Oncology at Mercy Hospital St. Louis.

    The powerful cyclotron produces proton particles, generating high-energy beams of protons to tumors. The proton therapy at Mercy Hospital St. Louis uses pencil beam scanning technology that has a targeted delivery system. It’s called a pencil beam because it’s only a few millimeters wide, the width of a pencil.

    “It’s the most precise form of external radiation therapy that we have,” said Dr. Frazier. “Since this is the newest proton center in Missouri, it has all of the state-of-the-art accessories you need to deliver precise radiation therapy.”

    Once delivered, protons interact with electrons in the atoms of cancer cells. A series of interactions result in damage to the DNA of the cancer cell, resulting in cell death and killing cancer. The cyclotron delivers the proton beam at hyper-speed with superior precision, sparing healthy tissue. Pencil beam proton therapy is used to treat complex cancers because of its unapparelled precision, which may be the only hope for some patients.

    “And so it’s ideal for patients who have tumors close to normal critical structures. So if a patient has a brain tumor that’s near the eye or their brain stem, proton therapy is great for that patient. And actually it’s great for a lot of patients,” said Dr. Frazier. “We can use proton therapy for lung cancer, esophageal cancer, patients with breast cancer. We use it for pancreas cancer, liver cancers, spine cancers. We can use it for prostate cancer. We can use it for any cancer in the body. We’ve seen patients who have received prior radiation and they were told by other radiation oncologists that they were not candidates for additional radiation. But with proton therapy, you can do that. You can treat just the tumor and keep the radiation off of those normal tissues that have already received radiation.”

    And proton therapy is beneficial for children with cancer.

    “Children  who have cancer – they’re more susceptible to the effects of radiation. So, if we can minimize the radiation to the normal tissues in a child, we need to do that.”

    The  Mercy Proton Therapy Center is a major accomplishment as it’s only one of 40 proton centers in all of the United States.

    It’s no wonder as the cyclotron, with all of its parts, takes up three full stories of building space .

    “This technology has required over eight decades of advancement and that’s because the first proton vault and the signature of the facility was over a football field inside,” said John Timmerman, PhD, Vice President of Operations at Mercy. “We’ve been able to shrink, through technology advancements, the size of the proton vault from a football field down to about 3,000 square feet.”

    “You have to have these massive arms to control the movement of that cyclotron,” explained Dr. Frazier. “Those arms are about 60 feet long and they’re about 30 feet wide at the end. That’s why it takes three stories in order to generate that proton particle. You have to have miles of tubing and miles of cable. Actually, there’s a thin wire on the inside of the cyclotron that’s 26 miles long. It’s super thin. But that allows us to then spin that proton around and around and then when it gets close to the speed of light, that’s when the beam comes out.”

    That’s what it takes to deliver the treatment into one proton therapy room, one patient at a time. The Mercy Proton Therapy Center is now open, treating its first patient on July 5th.