A combination of radiation therapy and immunotherapy may extend the immune responses to primary colorectal tumors and secondary tumors in mice, according to a study presented recently at the European Society for Radiotherapy and Oncology (ESTRO) 35 Conference.
Radiation therapy is commonly used to kill cancer cells and to activate the immune cells to recognize future proliferating malignant cells. However, this activation of the immune system is limited to the irradiated area and it’s often not strong enough to cure tumors.
Researchers have now combined radiation therapy with an immunotherapy agent (L19-IL2) in mice with primary colorectal tumors, showing that it strengthens the immune system, allowing for a more prolonged immune response that is not just restricted to the irradiated area.
“Radiation therapy damages the tumor, creating a sort of tumor-specific vaccine,” Nicolle Rekers, MSc, said in a press release. “It feeds the immune system and ensures that it notices that something is wrong. What is unique about our latest experiments is that we have been able to create a so-called abscopal effect, where a localized radiation treatment has also had an effect on other tumor sites outside this radiation field.”
Mice treated with this combination were found not only to be tumor free, but importantly, when they were re-injected with cancer cells 150 days following treatment, no new tumors were formed, possibly due to an increase in the amount of cells presenting an immunological memory.
“Of course, these mice are models of human disease and can never be 100 percent comparable with a patient, but the fact that the cured mice never formed new tumors, compared with a 100 percent tumor formation in untreated mice of the same age, is significant. We will know more after analyzing results from the Phase 1/2 clinical study in human patients that we started recently,” Rekers said.
The immunotherapy agent used, L19-IL2, combines an antibody against the tumor blood vessels and a cytokine, a molecule that is important for the immune system. It had already been shown to be safe in patients and the new trial will address the effects of the combination treatment in patients with solid tumors and multiple metastasis.
“We hope that this treatment will not only destroy tumors, but also enable the immune system to develop a memory that allows it to annihilate them in the future as well,” Rekers concluded.
ESTRO President Prof. Philip Poortmans also commented on the results presented at the conference.
“A couple of years after the first breakthrough of immunotherapy in medical oncology, we are now on the verge of an exciting new era that combines this novel approach with radiation therapy,” he said. “This could open the door to shorter treatment durations, thereby reducing side effects and costs compared to common palliative approaches in mono-immunotherapy, as well as to potentially new curative options where we had none before. It is time to join forces with all partners, including industry, to explore these capabilities.”