The effect of different radiotherapy regimen on the immune cell landscape

Immunotherapy is a relatively new form of therapy for the treatment of patients
with cancer. In this form of therapy, the own immune system is used to clean up
cancer cells, often in combination with other forms of treatment. Because the
body attacks the cancer cells, there is only a limited chance of side effects.
Immunotherapy is now considered the 4th pillar in the treatment of patients
with cancer, in addition to surgery, radiotherapy and chemotherapy. An
important next step is how we can best combine immunotherapy with the various
other forms of cancer therapy. More than half of the patients with cancer also
undergo radiotherapy during treatment. Recent studies in which radiotherapy and
immunotherapy are combined show promising results, but radiotherapy at the
wrong time or with the wrong dose can also reduce the immune response. To
investigate the optimal relationship between radiotherapy and the immune
system, we would like to characterize the immune cells in the blood and, if
possible, in the tumor. The status of our gut (microbiome) is also important
for the functioning of our immune system. By combining data from blood, tumor
and the intestine, we hope to be able to determine the optimal combination.

We want to investigate what happens to the immune cells during different types
of radiotherapy (schedules). With this study, we want to take blood samples
from patients during their standard radiotherapy for cancer and determine the
effect on immune cells. The effect of the radiation will also be examined in
tumor material that will be obtained via a second biopsy in a small part of the
patients during the irradiation, ie in easily accessible (oral) cancer.
Finally, we also want to examine the microbiome in the intestine during
radiotherapy. Insight into this will lead to the more specific giving of a
specific combination of radio- and immunotherapy.

Patients who visit the radiotherapy department of the Radboudumc for
radiotherapy of head and neck-, lung- or prostate cancer will be asked to
donate a few tubes of blood before, during and after treatment (3 to 5 times in
total, 60 ml per venipuncture). The patient is given time to decide on
participation during the preparation of the treatment plan etc (3-7 days). The
first blood sample will be drawn just before the first radiotherapy fraction. A
2nd venipuncture will be performed just before the 2nd fraction, and blood will
be taken one week after the last treatment. With the long treatment schedules,
we want to take 1 or 2 more blood samples. Immune cells will be characterized
by flow cytometry, including CD4, CD8 and regulatory T cells, Natural Killer
cells, MDSCs and macrophages. We will also look at the activation markers such
as CD28, CD137 and CD66b, and the inhibitory markers PD1, PDL-1, CTLA4. RNA
will be isolated for specific gene expression analyses or RNAseq. For oral
tumors we want to take a 2nd biopsy under local anesthesia. Here, too, we want
to characterize the immune cells with the help of immunohistochemistry for the
same markers. The microbiome will be characterized in stool samples taken
before and after radiotherapy.

The extent of burden due to 3-5 venepunctures is limited and the risk with
standard venapuncture is very limited. The biopsies in a small proportion of
patients will be taken under local anesthesia, and generate a small risk of
limited bleeding. Feces will be collected at home without risk to the patient.
This study has no effect on, or consequences for, the standard treatment.
Patients will not have to come to the Radboudumc for the blood samples as they
will be taken during the standard treatment schedule of the patients.