ESTRO 2024 - Abstract Book

S45 ESTRO 2024 standardization across the institutes. Recent rapid development of artificial intelligence accelerated the improvements of software applications and addressed problems that could not have been easily solved otherwise. The aim of this teaching lecture is to provide a helicopter view on several different aspects of IGPT, elaborate an optimal clinical solution for each of them and evaluate if the optimal solution have been already translated into broad scale clinical implementation. As image guidance in photon radiotherapy has long-standing tradition, the translation of the state-of-the-art imaging currently used in photon clinical practice into IGPT will be analysed. The clinical availability of innovative solutions will be explored. Moreover, the suitability of current IGPT for new emerging technologies will be addressed. The step-by-step demonstration of the current status will lead to a conclusion if the IGPT already enables to use the full potential of particle therapy or if the technology is still lagging behind. Invited Speaker

3355

Immunology: Should we not irradiate uninvolved nodes and blood pool?

Udo S. Gaipl

Universitätsklinikum Erlangen, Translational Radiobiology, Department of Radiation Oncology, Erlangen, Germany

Abstract:

Besides its DNA damaging effects on tumor cells resulting in local tumor control, radiotherapy (RT) has been proven

to modulate the immune system. But how does this work? During and following RT, components of the tumor cell

DNA are released into the cytoplasm, a place where nucleic acids should not be in a healthy state. This leads to the

activation of so-called DNA recognition signaling pathways, which ultimately change the immunological surface of the

cell and the microenvironment in order to activate the immune system, a mechanism originally evolved as defense

against viral and bacterial infections. Of course, this is the ideal scenario and the question arises why the immune

system is not always activated after RT and does not always attack all tumour masses in the body. One reason is that

RT has also immune suppressive effects, such as induction of TGF-beta and of increased expression of immune

suppressive immune checkpoint molecules (ICMs) on the tumor cell surface. This demands on the one hand for

combined treatments with immune therapies to take advantage of the immune stimulatory effects of RT and on the

other hand to preserve the immune system functions during and after RT.

To date, it is not yet known what is the most immunologically active (immunogenic) dose of RT. New RT techniques,

such as stereotactic body radiation (SBRT), allow higher single doses to be applied, but these do not necessarily have

to be more immunogenic. Although a high single dose releases more danger signals, it can also lead to the activation

of enzymes that degrade the DNA in the tumour cell cytoplasm, or immune-suppressing ICMs can occur to a greater

extent on the tumour cell surface. Further, irradiation of lymph nodes can have a negative effect, as these are the site

of the development of the adaptive immune response against the tumour. This could be one of the main reasons

why the studies on the combination of RT with immune checkpoint inhibition have not brought success in head and

neck cancer. In addition, the tumour masses at different sites in the body also differ in terms of their