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Flash Therapy

Radiation oncology innovations shrink treatment time for prostate cancer

May 22, 2018 | Dagny Stuart

Photo by John Russell


Instead of undergoing more than a month of radiation therapy for prostate cancer, Phillip Perry finished his treatments in just five days.

“The process was quick and I was able to carry on with my normal activities each day,” said Perry, a 53-year-old flight attendant from Mt. Juliet, Tennessee, who enjoys travel photography.

He is one of the first 60 patients at Vanderbilt-Ingram Cancer Center (VICC) to opt for an innovative therapy that combines high-dose radiation with a protective hydrogel that puts space between the targeted tumor in the prostate and healthy tissue in nearby organs.

“VICC has assembled a nationally recognized multi-disciplinary team of surgeons, medical oncologists and radiation oncologists who work together to provide a very personalized management approach, tailored to an individual patient’s tumor as well as wishes,” said Lisa Kachnic, MD, who leads the department and holds the Cornelius Vanderbilt Chair in Radiation Oncology.

For years, Perry suspected that he might have an elevated risk of developing prostate cancer. He had watched his own father cope with a prostate cancer diagnosis and the decision to undergo a then-experimental (and successful) treatment regimen.

So when Perry’s Vanderbilt University Medical Center (VUMC) primary care physician told him some families harbor a genetic risk factor that makes men more susceptible to the disease, he agreed to regular tests to measure the prostate-specific antigen (PSA) in his blood. After years of normal results, the PSA numbers started escalating and that’s when Perry told his physician he wanted to be proactive and undergo further testing.

“Less than a year before that I lost my stepfather to prostate cancer because, unfortunately, he ignored everything. By the time he sought medical help it had already spread…it was very painful to watch such a vibrant man lose everything including his life,” Perry said.

Determined to avoid that fate, Perry consulted a team of VUMC physicians who collaborated on a plan to assess his disease profile and then recommend the best treatment options.

Sam S. Chang, MD, who holds the Patricia and Rodes Hart Chair in Urologic Surgery, performed the biopsy that confirmed those rising PSA numbers weren’t a fluke. Perry had a small cancerous tumor that hadn’t yet spread beyond the prostate.

Given a choice of treatment options, Perry decided to undergo the innovative form of radiation therapy. He was among the 2,340 patients consulted for treatment last year by the radiation oncology specialists at VICC. Many patients travel great distances to access the expertise and leading-edge technologies provided by this expanding department, headed by Kachnic, nationally recognized for her research and currently serving as president of the American Board of Radiology, one of the independent national boards comprising the American Board of Medical Specialties.


The treatment

Eric Shinohara, MD, MSCI, associate professor and vice chair of Radiation Oncology, was the expert Phillip Perry chose to plan and execute the treatment regimen for his cancer. Shinohara recommended SBRT, a form of radiation therapy that delivers a high-dose, focused beam of radiation to the tumor.

“In many ways we’re trying to replicate what a surgeon can do with this very focused radiation treatment. We can be incredibly accurate so that the tumor can be treated while avoiding normal organs in the area,” Shinohara explained.

Eric Shinohara, MD, MSCI, medical director of Radiation Oncology, treated Phillip Perry for prostate cancer. Photo by John Russell.

Another advantage of SBRT is the short timeframe needed to administer the therapy. What used to take 44 daily sessions can now be done in just three to five days depending on the type of tumor.

VICC is already using SBRT to treat lung cancer, as well as tumors in the liver, pancreas, brain and spinal cord. The technology also can be used to deliver radiation to tumors that have spread or metastasized to the bone, reducing the pain.

Prostate cancer is one of the newer uses for SBRT and Shinohara said there is a growing body of research showing that it is safe and effective if done correctly. A new hydrogel spacer that protects nearby tissues increases the safety of the technique.

“It’s basically like an epoxy. You inject two syringes of materials that mix together and harden into a type of jelly, creating a space between the rectum and the prostate, so we can dramatically reduce the radiation dose to nearby tissues and reduce unwanted side effects,” Shinohara said.

The hydrogel remains stable during radiation therapy and then is gradually absorbed by the body after the treatments have been completed.

“You never know it’s there and there’s no discomfort from it,” said Perry, who underwent treatment in September 2017.

As the effects of the radiation wore off in the following weeks, he was relieved to discover that he had no lasting urinary or bowel issues.

“It truly was kind of remarkable because you’re always hearing about the side effects. You always have it in the back of your mind; it could happen to me, this is real. So you are very relieved when you don’t have those side effects.”

He was also pleased with the “wonderful doctors” and the rest of the VICC team who diagnosed and delivered his care.

“The staff just made it so easy, so much easier than I ever thought it would be. All of this has worked out and this was the best team I could ever dream of or encounter in my situation. I was extremely happy with everything that I went through,” Perry said.


The physics

Those team members include Michael Price, PhD, DABR, vice chair and director of Physics in the Radiation Oncology department. Price, who received his doctorate from University of Texas MD Anderson Cancer Center, leads the team of medical physicists who “make sure that the machines that deliver focused radiation are functioning correctly and within specifications.”

They also perform calculations to determine how much radiation is delivered and how to use the revolutionary SBRT technology to accomplish their goals.

The department utilizes the newest generation of radiation-delivery machines, medical linear accelerators, to produce radiation beams with amazing accuracy.

“It’s like a heat, or laser-guided missile, akin to a Star Wars ray gun. The precision with which we are able to deliver the therapy is almost unlimited. You’re able to deliver a high dose to a very specific tumor area while avoiding everything that’s healthy around it,” Price said.

This accuracy enables the radiation to be targeted at tumors perched in a precarious place in the body, or wrapped around a vital organ.

“If there’s a tumor behind the eye, you want to preserve the patient’s vision. If a tumor is right next to the brain stem, we need to protect other critical areas of the brain. For breast cancer, we want to minimize the amount of heart that we irradiate and we have the ability to do that with the machines that we use and all of the ancillary systems that are used for imaging the patients during radiation treatment,” Price said.

The new linear accelerators, which rotate around the patient, feature metal “leaves” that move in and out at set times to shape the beam. They also have imaging devices that allow team members to view the organ being treated as well as the surrounding normal tissues.

“The metal leaves, or MLCs, allow us to precisely shape the radiation to the organ or tumor, while limiting any radiation dose to the normal surrounding structures. We then use a form of on-board CT imaging to assure that we are treating the tumor with pinpoint accuracy. The imaging also allows us to see shrinkage of the tumor as a patient’s treatment progresses,” Price said.


The horizon

Unraveling the mystery of how a small clump of cells grows into a malignant mass, how those tumors spread, and how they respond to radiation and other treatment is the focus of research by VICC radiation oncology experts. Austin Kirschner, MD, PhD, assistant professor of Radiation Oncology, treats patients and operates a research laboratory. He has focused his energy on combining radiation with other types of therapies.

“We have specialized equipment that allows us to deliver radiation for research models whether they’re in cell cultures, incubator-style tissue cultures or in mice. In this manner, we can experiment with radiation in a living system and that’s essential to learn the mechanisms of radiation treatment with different chemotherapies or biologic medicines,” Kirschner said.

The newest riddle is how best to combine radiation with immunotherapies, especially checkpoint-inhibitor drugs that work by targeting a molecular switch that stimulates the immune system to attack cancer cells. Radiation has been shown in early mouse studies to also stimulate the immune system, especially in high radiation doses, similar to that used in the SBRT treatments. The conundrum is whether it’s best to start with the immune drug followed by radiation or the reverse sequence, as well as what radiation and drug doses are best to combine.

“We’ve undertaken lab projects in which we model this question in mice.

“No one knows what the magic combination or sequence is, and it is likely that this answer may be dependent on tumor type. Although cancer biology is variable, we hope to model this radiation immune effect and provide some insight on the best delivery strategy,” Kirschner said.

Much of his research is focused on prostate cancer.

“We’ve figured out a reliable combination of radiation and an immune checkpoint drug for prostate cancer, but we’re still optimizing the dosing to achieve maximal tumor shrinkage and survival in the mice,” Kirschner said. “Once optimization is complete, we will be translating these efforts into developing a clinical study for men with prostate cancer.”

Kachnic said her team is at the forefront of innovative care.

“This combination of revolutionary research and leading-edge technology is the hallmark of VICC’s radiation oncology enterprise,” Kachnic said. “We have put together a team of nationally recognized experts to provide our patients with exceptional personalized care.”