ESTRO 2020 Abstract book

S145 ESTRO 2020

contexts in eliciting cell-autonomous innate immune phenotypes in response to PARPi. Loss of ERCC1, per se , resulted in enhanced STING expression and type I IFN transcriptomic signature in NSCLC cells, and low ERCC1 expression correlated with increased lymphocytic infiltration in human NSCLC samples. Conclusion : Our data suggest that PARPi that could be therapeutically exploited in combination with certain immunotherapies in appropriately selected populations, such as patients with BRCA1 -mutant TNBC or ERCC1 - defective NSCLC. The corresponding academy-sponsored clinical trial, which we developed in our institution and other cancer centers in France, is underway (EUDRACT N°2018-001744-62). SP-0259 ATR inhibitors can modulate the immune tumour microenvironment after radiation M. Dillon 1 1 Institute of Cancer Research, Chester Beatty Laboratories, London, United Kingdom Abstract text ATR inhibitors (ATRi) are effective radiosensitisers in vitro and in vivo [1]. Clinical trials are in progress to examine safety and efficacy of combined ATRi and radiation [2]. Emerging data show that ATRi may also cause significant modulation of the immune tumour microenvironment when combined with radiotherapy [3]. Data on micronucleation, changes in cellular infiltration from in vivo models and early clinical results will be presented. 1. Radiosensitization by the ATR Inhibitor AZD6738 through Generation of Acentric Micronuclei. Mol Cancer Ther, 2017. 16(1): p. 25-34. 2. PATRIOT: A phase I study to assess the tolerability, safety and biological effects of a specific ataxia telangiectasia and Rad3-related (ATR) inhibitor (AZD6738) as a single agent and in combination with palliative radiation therapy in patients with solid tumours. Clin Transl Radiat Oncol, 2018. 12: p. 16-20. 3. ATR Inhibition Potentiates the Radiation-induced Inflammatory Tumor Microenvironment. Clin Cancer Res, 2019. 25(11): p. 3392-3403.

while others progress fast and advancement of systemic therapies may lead to control of systemic disease with devastating progressive intracranial disease. It is imperative that the treatment approach should be based on multidisciplinary discussion, taking into account survival benefit, patient’s wishes, quality of life and survival. SP-0262 Management of extracranial disease with stereotactic radiotherapy A. Kirby 1 1 Royal Marsden & Institute Cancer Research, Radiotherapy, London, United Kingdom Abstract text This presentation will review the rationale for SBRT in patients with low metastatic burden disease and the potential clinical settings in which SBRT can be applied. Data relating to oncological and toxicity endpoints will be presented and the current clinical and trial landscape reviewed. SP-0263 What is the optimal dose and fractionation? M. Hawkins 1 1 University College London, Dept. Of Medical Physics And Bioengineering, London, United Kingdom Abstract text The role and timing of radiotherapy in pancreatic cancer is subject to controversy and there is debate regarding the dose schedule. For patients with borderline resectable pancreatic cancers neoadjuvant therapy regimen of systemic chemotherapy followed by conventionally fractionated RT (25 fractions) with chemotherapy, moderately hypofractionated (15 fractions) of stereotactic ablative radiotherapy (SBRT) 5 fractions are accepted schemes. For patients with locally advanced pancreatic cancer, not suitable for surgery despite a definitive therapy regimen of systemic chemotherapy, there are three main approaches: conventionally fractionated radiotherapy with concurrent chemotherapy, dose- escalated fractionated chemoradiation, or multifraction SBRT without chemotherapy. Ongoing and published clinical trials are testing and supporting the various doses and fractionations. As systemic treatments are improving the outcomes in pancreatic cancer, radiotherapy continue to play a key role in controlling local disease, and multidisciplinary team discussion is necessary for selecting the best radiation dose and schedule combination in each setting. Symposium: The role of radiotherapy in locally advanced pancreatic cancer

Symposium: Multimodal approach to oligometastatic breast disease: current state-of-the-art

SP-0260 Treatment of oligometastatic breast cancer based on biology S. Rivera Institut Gustave Roussy, Villejuif, France

Abstract not received

SP-0261 Unknown to the unknown: breast cancer brain metastases O. Kaidar-Person 1 1 Sheba Medical Center, Radiation Oncology, Ramat Gan, Israel Abstract text The management of breast cancer patients with brain metastases should be in correlation with the breast cancer molecular subtype, status of systemic disease, and other prognostic factors. Treatment is often challenging as there are different modalities available; different disease “behaviors” with some patients having indolent disease

SP-0264 What is the target volume? F. Huguet Hôpital Tenon. Paris Cedex, France

Abstract not received