Irradiating only a portion of the lymph nodes significantly reduces the recurrence of several cancers

A promising new study released by the University of Colorado Cancer Center shows that recurrence of certain cancers can be significantly reduced by irradiating only a group of lymph nodes near a tumor, rather than all of them
.

The study was published today in
the journal Nature Communications.

Dr.
Sana Karam, associate professor of radiation oncology at the University of Colorado School of Medicine and senior author of the study, said: "Traditionally, doctors irradiate all lymph nodes around a tumor in a process called 'selective lymph node irradiation
.
' But in the age of immunotherapy, the problem with this scorched earth approach is that doing so also eliminates the source
of immune cells for immunotherapy.
Lymph nodes are hubs that activate and expand the main immune cells that fight cancer
.
”

Karam and her team learned that radiation therapy to all lymph nodes around the tumor significantly reduces immune memory and antigen spread, thereby increasing the risk of
tumor spread far from the tumor's primary site.
It was an unexpected discovery
.

The team conducted preclinical tests
on several different head and neck tumor models, as well as breast cancer and melanoma models.
No matter what kind of cancer is treated, the outcome is the same
.
When radiation kills immune cells that recognize cancer, the patient's immune system loses the system's ability to
fight cancer.

On the other hand, researchers have found that irradiating certain lymph nodes called sentinel lymph nodes is absolutely critical
.
If irradiation fails, it will cause recurrence
nearby.
"This study confirms why selective lymph node irradiation has long been the standard of care because it does reduce local recurrence," said
Laurel B.
Darragh, first author of the paper.
"But it also suggests that in order to effectively combine radiotherapy and immunotherapy, we need to re-evaluate our strategy to limit nodal irradiation
to sentinel lymph nodes.
" This eliminates local recurrence and distant transmission of the neck while maintaining a long-term systemic immune response
.
”

Data from a recent human clinical trial confirmed this finding that preoperative radiotherapy was limited to large tumors and sentinel lymph nodes, while avoiding all other lymph nodes to maintain immune memory
.
The researchers found that the immune systems of these patients were highly activated, which has been shown to be associated with
a better prognosis.

"We hope that these data will lay the groundwork for future clinical trial designs that not only reduce side effects in patients, but also improve long-term outcomes," Karam said
.