Adding an immune system-strengthening compound to radiation therapy can extend the immune response that the radiation therapy induces, so that both irradiated tumor sites and tumors outside the radiation field are affected. These findings, using the L19-IL2 immunotherapy agent in mice, were presented at the ESTRO 35, the 2016 annual meeting of the European Society for Radiotherapy and Oncology.1
An immune response is known to be initiated by radiation therapy. However, it is often not sufficient to cure tumors and its effect is limited to the area that has been irradiated.
This research combined radiation therapy and L19-IL2, which is a combination of an antibody that targets tumor blood vessels and a cytokine, a small protein involved in cell signaling in the immune system.
After treatment, mice were tumor-free. Furthermore, when the treated mice were re-injected with cancer cells after treatment, they did not form new tumors. In contrast, 100% of untreated mice formed new tumors. The number of cells with an immunologic memory increased in the treated mice.
“Radiation therapy damages the tumor creating a sort of tumor-specific vaccine,” said Nicolle Rekers, MSc, from the Department of Radiation Oncology, Maastricht University Medical Centre, Maastricht, The Netherlands, in her presentation.
“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.”
A phase I/II clinical study in human patients was recently started. It will look at the combination treatment in patient with oligometastatic solid tumors.
“Our ultimate aim is to increase the time during which the disease does not progress by using this combination to bring about an immune response that will attack both the primary tumor and its metastases,” said Rekers.
Reprogramming the immune system appears to not have damaging long-term effects, based on research to date on this fairly new approach.
“We believe that the risk/benefit equation is likely to come down firmly on the side of benefit. 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,” concluded Rekers.
1. Rekers NH, Yaromina A, Lieuwes NG, et al. Radiotherapy and L19-IL2: perfect match for an abscopal effect with long-lasting memory. Presentation at: ESTRO 35; April 29-May 3,2016; Turin, Italy. Abstract OC-0234.