ESTRO 2023 - Abstract Book

S275

Sunday 14 May 2023

ESTRO 2023

SP-0355 Towards precision use of radiation therapy with immunotherapy S. Demaria 1 1 Weill Cornell Medicine, Radiation Oncology, New York, USA

Abstract Text A large body of preclinical data supports the ability of radiation to modulate cancer cell intrinsic immunogenicity as well as the tumor immune microenvironment and increase responses to immune checkpoint inhibitors (ICI). Early reports of recovered responses to ICI in patients receiving radiation therapy (RT) have raised a lot of enthusiasm for the potential of radiation to benefit patients beyond its traditional role in local cancer control or palliation. Prospective clinical trials testing combinations of RT with ICI have provided proof-of-principle evidence that radiation can induce tumor-specific T cell responses in patients treated with ICI. However, evidence that adding RT to ICI provides a reproducible benefit has been for the most part elusive in randomized trials. This gap in translation highlights gaps in knowledge about the factors that affect the anti-tumor immune response to RT+ICI combinations. It is becoming clear that the role of radiation-specific factors (such as dose, fractionation and field), as well as tumor- and host-specific factors need to be better understood in order to harness radiation’s new role as an adjuvant to cancer immunotherapy. I will briefly summarize our experience in characterizing the mechanisms that are central to RT ability to increase responses to ICI in mice and patients, and present new insights about the signals from irradiated cancer cells that activate interferon type I in antigen-presenting cells, a key requirement for in situ vaccination by radiation. Our recent single cell analysis in preclinical models highlights the fact that there are qualitative and quantitative changes in the intratumoral T cell compartment in tumors treated with RT plus anti-CTLA4 that cannot be predicted by analyzing the effects of each individual treatment. Finally, our preclinical data show that RT is necessary but often not sufficient to induce responses to ICI in the majority of tumor-bearing hosts, and additional treatments targeting pre-existing or RT-induced barriers are required. Overall, these data can help the design of clinical studies that test precision combinations of RT and immunotherapy and provide better and more reliable clinical benefits to patients.

SP-0356 Low dose radiotherapy reverses resistance to immunotherapy: From bench to bedside F. Herrera Switzerland

Abstract not available

SP-0357 Radiomics to predict outcomes of patients treated with immunotherapy combinations P. Lambin

Abstract not available

Joint Symposium: ESTRO-EANO: Changing the landscape for multidisciplinary treatment of brain metastases

SP-0358 Pre- vs post-operative radiotherapy for brain metastases J. Biau France

Abstract not available

SP-0359 Up-front vs. delayed radiotherapy in the context of new approaches to immunotherapy M. Lorger

Abstract not available

SP-0360 Whole brain radiotherapy vs radiosurgery for multiple brain metastases J. Zindler 1 1 Haaglanden Medical Centre, Radiotherapy, The Hague, The Netherlands

Abstract Text There is an increasing number of systemic therapies to treat brain metastases of large cell cancers. Trials have showed that whole brain radiotherapy (WBRT) has a detrimental effect on neurocognitive function and quality of life compared to best supportive care. Therefore the indication of WBRT for multiple brain metastases is a matter of debate. Technical advances have made stereotactic radiotherapy (SRT) available in routine clinical practice also for multiple brain metastases. This treatment is attractive in the setting of effective systemic therapies such as immunotherapy and targeted agents, because of its high local tumor control and avoidance of elective brain irradation. This presentation discusses the role of SRT for multiple brain metastases in the modern multimodality treatment of brain metastases.

SP-0361 Hippocampus sparing for PCI and WBI - Ready for primetime? J.L. Lopez Guerra 1 1 University Hospital Virgen del Rocio, Radiation Oncology, Seville, Spain

Abstract Text