A promising new study from the University of Colorado Cancer Center indicates that the recurrence of some types of cancer can be significantly reduced by irradiating only a select group of lymph nodes near the tumor rather than all of them.
The study was published today in Nature Communications.
“Traditionally, doctors irradiated all the lymph nodes surrounding the tumor in a process called ‘elective nodal irradiation,’” said Sanaa Karam, MD, associate professor of radiation oncology at the University of Colorado School of Medicine and senior author of the study. Immunotherapy is because doing so also kills off the source of immune cells for the immunotherapy to work on. Lymph nodes are the hub for creating and expanding key immune cells that can go and fight cancer.”
Karam and her team learned that irradiating all the lymph nodes around the tumor with radiation significantly reduces immune memory and antigen spread, creating a much greater risk of cancer spreading to parts of the body far from the original tumor site. “This was an unexpected result,” says Karam.
The team tested this preclinical theory on several different tumor models of the head and neck, along with a model of breast cancer and melanoma. The result was the same regardless of the type of cancer being treated. When the radiation killed the immune cells that could recognize the shape of the cancer, the patient’s immune system lost the ability to fight the cancer systemically.
On the other hand, the researchers found that the irradiation of certain lymph nodes known as sentinel lymph nodes is crucial. Failure to irradiate those resulted in a close recurrence.
Dara, first author of the paper and an MD/PhD student in Dr. Karam’s lab: “This study confirms why elective nodal irradiation has long been the clinical standard of care, as it reduces regional recurrence.” “But it also shows that to effectively combine radiation with immunotherapy, we need to re-evaluate our strategies and limit nodal irradiation to the sentinel lymph nodes. This eliminates localized neck recurrence, and distant spread, while preserving the long-term systemic immune response.”
The results are confirmed by data from a recent human patient clinical trial in which preoperative radiation was restricted to the gross tumor and sentinel lymph nodes while sparing all other lymph nodes to preserve immunological memory. The researchers found that these patients had a very active immune system, which has been shown to be associated with a better prognosis.
“We hope that this data will pave the way for the design of future clinical trials, not only to reduce side effects for patients but also to improve long-term outcomes,” Karam said.