ESTRO 2021 Abstract Book

S160

ESTRO 2021

Abstract not available

Teaching lecture: The future of RTT advanced practice

SP-0233 The future of RTT advanced practice Y.M. Tsang 1 1 Mount Vernon Cancer Centre, Radiotherapy, Northwood, United Kingdom

Abstract Text Radiation therapists (RTT) are responsible for planning and delivering radiotherapy (RT) and play a non- replaceable role in cancer patients’ RT pathways. Task shifting is a strategy where a professional group, that generally requires less training and fewer qualifications, expands their scope of practice to close gaps with other professional groups that requires longer training, in order to tackle bottlenecks or gaps in the delivery of high quality and timely care to patients. For the purposes of streamlining workflows in RT, this task shifting concept has been consolidated under the umbrella of ‘advanced practice’ (AP). There is no doubt that each AP position is unique. The concepts of task shifting through AP roles should not be interpreted as replacing medical colleagues but rather as a way to rationalize who provides what service, in order to augment the efficiency and effectiveness of our healthcare system for patients getting the right care at the right time. The development of AP in RT is constantly progressing locally and globally. AP can quickly be perceived as ‘standard’ practice. It is important to consider that AP roles should adapt over time due to the continuously evolving technology and service needs. Against this background, this presentation aims to discuss what the future of RTT AP lies in front of us; and how we can strive for gathering all relevant information in a consistent manner and provide evidence that will compel healthcare service users and RT departments to implement clinically relevant AP roles.

Symposium: Turning cold into hot tumours: Challenges in radio-immunotherapy

SP-0234 Radiotherapy and Immunotherapy Combinations: The Hype and the Hope R . Weichselbaum University of Chicago, Radiation and Cellular Oncology, Chicago, USA

Abstract Text I will review the fundamental underlying principles of the interaction(s) between radiotherapy and immunotherapy as well as the results of randomized and selected phase 1 and 2 trials that combined radiotherapy and immune checkpoint inhibitors. The results of two randomized trials of adjuvant immunotherapy following chemo/radiotherapy demonstrated improved outcomes whereas concurrent chemo/radiotherapy/immunotherapy in head and neck cancer did not improve outcome. Results of large phase 1 and 2 trials demonstrate a hint that patients who receive single or “several site” radiation may benefit from the addition of immunotherapy; however, the results suggest that any improvement in outcome is likely restricted to a small subset of patients and the induction of a clinically meaningful abscopal effect is almost entirely absent from these trials. Also, there is little evidence for the current dogma regarding fraction size and the induction or suppression of an immune effect. I propose one avenue of investigation is to treat all sites of disease with potentially curative doses of radiation, which takes advantage of the cytoreductive power of radiotherapy and possibly enhances the anti-tumor effects of immunotherapy within the tumor microenvironment.

SP-0235 How to boost the abscopal effect S. Formenti 1 1 Weill Cornell Medicine/NewYork-Presbyterian Hospital, Radiation Oncology, New York, USA

Abstract Text How to boost the abscopal effect Silvia C Formenti, Weill Cornell Medicine, New York, NY

Radiation (RT) has revealed to be ideal partner to immunotherapy to enhance cancer immunogenicity. In response to DNA damage, cytosolic DNA released from the nucleus and mitochondria activates sensors like cGAS/STING, leading to release of IFNβ, that recruits and activates BAFT3 + dendritic cells, for cross- presentation and cross-priming of CD8 + T cells ( Deng L et al, Immunity 2014; Vanpouille-Box C et al, Nature Communications 2017; Yamazaki T et al, Nat Immunol. 2020) . Radiation has multiple other immunogenic effects, including increasing the trafficking of activated CD8 + T cells by releasing CXCL16, a chemokine that binds to CXCR6 (Matsumura et al., J Immunol, 2008) . Recent evidence has demonstrated how as part of DNA damage response to radiation, mutated cancer genes are expressed, availing neoantigens to the patient’s immune system (Formenti S et al, Nature Medicine, 2018; Lhullier C et al, JCI 2021). By recruiting both the innate and adaptive immune response RT can convert the irradiated tumor into an in situ vaccine, providing the host with a tumor specific immune response that both contributes to the response of the irradiated tumor and potentially, unirradiated metastasis, a rare clinical occurrence initially described by Mole et al. as the abscopal effect (Mole RH. Br J Radiol. 1953). Our team has originally linked the immunogenicity of RT with the abscopal effect ( Demaria et al IJROBP, 2005) and over the past twenty years investigated how to enhance it, by testing focal RT in combination with different immunotherapy strategies, with promising preclinical and clinical results. The rarity of abscopal effects when RT is used alone, is easily explained by the multiple immunosuppressive