PHILADELPHIA (August 10, 2020)—In a recent study, researchers at Fox Chase Cancer Center found that prostate tumor growth was delayed in mouse models when treated with specific types of radiodynamic therapy.
Researchers evaluated the novel use of high-energy photon radiation with 5-aminolevulinic acid (5-ALA), a photosensitizing drug, and carbamide peroxide for effectiveness against prostate cancer in a mouse model. Elements of the radiodynamic therapy were similar to those used in photodynamic therapy treatment, which uses light to react with a chemical that is topically applied to the skin.
“One of the reasons photodynamic therapy is so limited is because when you use visible light, you can’t really get far into the body,” said Joseph Panetta, PhD, lead author on the study. Panetta is a medical physics resident in the lab of Chang-Ming Charlie Ma, PhD, FASTRO, professor and vice chairman in the Department of Radiation Oncology at Fox Chase.
“Recently, the field has tried to explore radiodynamic therapy, which is basically the same principle, only the light we use is something we can get into the body as opposed to just the surface,” Panetta said. “This way, if you have a tumor in, for example, your liver, it can go all the way into the body. This light is called Cherenkov radiation, which is a blue light that can be generated by high-energy radiotherapy beams in the patient’s body.”
In the study, mice were injected with human prostate cancer cells and randomized into eight treatment groups with various combinations of radiotherapy beams, 5-ALA, and carbamide peroxide.
Researchers found that radiodynamic therapy significantly delayed the tumor growth for the mouse model and tumor cell line compared to other treatments. Peroxide and 5-ALA did not contribute significantly to tumor growth delay when administered alone or separately with radiotherapy, according to the study authors.
“We were happy to see the results, but would like to see a more dramatic improvement. We hope that by tweaking how much of the drug we use or the timing and the energy of the radiation beam, we can get a more dramatic effect,” said Panetta. He added that the next steps would be to use an LA45 accelerator, which is a unique radiotherapy device acquired by Fox Chase to investigate radiodynamic therapy.
“The hypothesis is that if we use higher energy beams from this accelerator, we’ll have a more dramatic effect, because higher radiation energies produce more blue light. This blue light, we think, is one of the reasons the drugs are activated in the body,” Panetta said.
A phase 1 clinical trial to test radiodynamic therapy using LA45/5-ALA has received Food and Drug Administration and institutional review board approval and is expected to enroll patients soon, Ma added.
The study, “Radiodynamic Therapy Using 15-MV Radiation Combined With 5-Aminolevulinic Acid and Carbamide Peroxide for Prostate Cancer In Vivo,” was published in the journal Physics in Medicine and Biology.