Treating colorectal cancer with radiotherapy kills cancer cells and makes subsequent immunotherapy more effective.
Radiation therapy fights cancer in more ways than one.
Not only does radiation force cancer cells to self-destruct, but several studies demonstrate that it also activates the body’s immune system to attack tumor cells. This activation can be used to boost current immunotherapies, such as anti-tumor vaccines, to produce better clinical results.
What’s less clear, however, is exactly how to combine the two therapies to get the best bang for the therapeutic buck.
To address this question, clinical researchers at the Kimmel Cancer Center at Jefferson tested an experimental cancer vaccine in combination with radiation therapy in mice with colorectal cancer. In research published online in the International Journal of Radiation Oncology, the researchers reported that the colorectal cancer vaccine was most effective when tumors were irradiated first and then the vaccine was administered a week later.
“Prior to these experiments, we didn’t appreciate the impact that sequencing of these treatments had on their combined ability to generate immune and clinical responses,” says Jefferson radiation oncologist Matthew Witek MD, first author of the study. “Remarkably, immune activation and tumor regression only occurred when radiation was given prior to vaccination.”
When mice received either treatment alone, the researchers noticed only a modest reduction in tumor size. However, when radiation was given first, the investigators saw a six-fold increase in cancer-fighting immune cells, and impressively, complete remission of the majority of tumors.
Although the work will need to be reproduced in humans to determine if the same holds true for cancer patients, the finding is exciting, says lead researcher Adam Snook, PhD, an instructor in Jefferson’s Department of Pharmacology and Experimental Therapeutics. “In a patient population that will undergo radiation therapy as standard treatment, these results provide a roadmap to amplifying the effects of immunotherapies like the one we’re developing for colon cancer.”
Targeted Diagnostics & Therapeutics, Inc, which provided research funding that, in part, supported this work, has a license to commercialize inventions related to this work.
This work was supported by grants from the National Institutes of Health (RC1 CA146033, P30 CA56036, R01 CA170533), the Pennsylvania Department of Health (SAP #4100059197, SAP #4100051723), and Targeted Diagnostic and Therapeutics Inc.
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