Radiation therapy plus immunotherapy can destroy both primary and secondary tumors, according to research presented at the European Society for Radiotherapy and Oncology (ESTRO) conference.
Radiation therapy not only kills cancer cells, but also helps to activate the immune system against their future proliferation. However, the immune response is often not strong enough to be able to cure tumors, and even when it is, its effect is limited to the area that has been irradiated. But the addition of a compound that strengthens the immune system can extend the immune response, and this response even has an effect on tumors outside the radiation field.
A combination of radiation therapy and L19-IL2, an immunotherapy agent, significantly increased immune response when given to mice with primary colorectal tumors. L19-IL2 is a combination of a cytokine and an antibody that targets the tumor blood vessels.
The researchers found not only were the mice free of tumors following treatment, but also they did not form new tumors when reinjected with cancer cells 150 days after treatment. There was also an increase in the number of cells with an immunological memory.
The lifespan of mice is quite short -- about two years -- so 150 days is a relatively long time.
"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," said Nicolle Rekers from the department of radiation oncology at Maastricht University Medical Center in Maastricht, the Netherlands. "We will know more after analyzing results from the phase I/II clinical study in human patients that we started recently."
The new trial will look at the combination treatment 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.
