Radiation Therapy and Immunotherapy Combo Increases Response to Colon Cancer

Immune response that attacks tumors may significantly improve progression-free survival.

A combination of radiation therapy and immunotherapy significantly increased the immune system response in mice with colorectal tumors, a recent study found.

Radiation therapy is frequently used because it kills cancer cells while helping activate the immune system against future proliferation. However, the immune response is often not strong enough to cure the tumors, and even when it is, the effect is limited to the area that has already been irradiated.

A study addressing these issues was presented recently at the ESTRO 35 conference.

During the study, researchers used a combination of radiation therapy and the immunotherapy agent L19-IL2 to treat mice with colorectal tumors.

The results of the study showed that mice were tumor free after treatment. Additionally, when the mice were re-injected with cancer cells 150 days after the cure, no new tumors formed.

Furthermore, there was an increase in the amount of cells with an immunological memory, according to the study.

“Radiation therapy damages the tumor creating a sort of tumor-specific vaccine,” said researcher Nicolle Rekers, MSc. “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.”

Although the study was performed on mouse models containing the human disease, the results were still promising.

“Of course, these mice are models of human disease and can never be 100% comparable with a patient, but the fact that the cured mice never formed new tumors, compared with a 100% tumor formation in untreated mice of the same age, is significant,” Rekers said. “We will know more after analyzing results from the Phase 1/2 clinical study in human patients that we started recently.”

L19-IL2 is known to be safe in people with only mild side effects that are limited to injection site reactions and the new trial will evaluate the combination treatments in patients 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,” Rekers said.

Researchers hope the treatment will destroy tumors, in addition to enabling the immune system to kill the cancer in the future through immunological memory. Additionally, they believe that the benefits versus the risks for reprogramming the immune system will change and lean more towards a beneficial result.

“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,” said ESTRO President Philip Poortmans. “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.”