ESTRO 2020 Abstract book

S5 ESTRO 2020

cancer genetic alterations on the clinical responses to irradiation remains a major obstacle in the implementation of personalized radiotherapy. Here, we report on a large-scale profiling effort to identify and classify mutant alleles that govern radiation survival. Our results reveal new insights into the mechanisms of cellular survival to radiation and genome maintenance during therapeutic stress.

SP-0022 Against the motion (against ENI) G. De Meerleer KU Leuven, Department of Radiotherapy and Experimental Cancer Research, Belgium

Abstract not received

Debate: This house believes that upfront radiotherapy is mandatory in patients with brain mets even in the era of immunotherapy

Debate: This house believes that Elective nodal radiotherapy should be performed for high risk prostate cancer

SP-0023 For the motion S. Combs (Germany) Klinikum rechts der Isar, TU München, Germany

SP-0019 For the motion (for ENI) Elective Nodal for High Risk Prostate Cancer

Abstract not receievd

M. Roach 1 1 UCSF, Radiation Oncology, San Francisco, USA

SP-0024 Upfront radiotherapy in not mandatory in patients with brain metastases treatable with immunotherapy or targeted therapies R. Soffeti 1 1 University of Torino, Neuro-Oncology, Torino, Italy Abstract text There is an increasing evidence that, in the era of effective immunotherapy with checkpoints inhibitors or targeted agents against driver mutations in melanoma and NSCLC, radiotherapy, either stereotactic radiosurgery or whole- brain radiation therapy, can be delayed at salvage to minimize the risk of cognitive deficits in long-surviving patients. In this regard some points seem to be clear. Immunotherapy with either ipilimumab alone or ipilimumab combined with nivolumab is indicated as initial treatment in patients with brain metastases from melanoma who are not BRAF mutant and do not need steroids. Immunotherapy with pembrolizumab is indicated as initial treatment in patients with small and asymptomatic brain metastases from NSCLC without druggable molecular alterations and with PDL1 expression. Patients with small and asymptomatic brain metastases from EGFR-mutant and ALK-rearranged NSCLC or BRAF- mutant melanoma should receive targeted agents as initial therapy. SP-0025 Upfront radiotherapy is mandatory in patients with brain mets even in the era of immunotherapy N. Andratschke 1 1 University Hospital Zürich, Department of Radiation Oncology, Zurich, Switzerland Abstract text Brain metastases are common events in the natural course of many metastasized solid cancers like breast, lung and renal cancer or melanoma with a cumulative risk of 10-30% in adults. In recent years, novel systemic treatment strategies have been developed and this has impacted on the general management of brain metastases. Although formal comparative level I evidence is still missing, radiotherapy as the mainstay in brain metastases management is being challenged.As a pro discussant I will support the role of early integration of SRS in the management of brain metastases, especially in the light of recent developments in oligometastasis and repeat SRS for multiple brain metastases, and critically discuss systemic only approaches.

Abstract text Elective nodal radiation (ENI) is a standard component of treatment for patients undergoing definitive irradiation for many solid tumors, including: gynecologic, rectal, head & neck and bladder cancers. With the development of technologies that allowed higher doses to be delivered to the prostate, some investigators became convinced this obviated the need to treat regional disease, despite the known pattern of spread and the policies adopted by urologist that there was a need to address nodal disease. For example, AUA guidelines recommend a lymph node dissection be performed in patients with a risk of lymph node involvement exceeding 2%. Essentially all the early phase III randomized trials establishing the role of ADT with external beam radiation (EBRT) included elective nodal irradiation (ENI) (e.g. RTOG 8531, 8610, 9202 and EORTC 22863, 22961). The two largest phase III trials addressing ENI (neither powered for a survival endpoint) demonstrated that neoadjuvant hormonal therapy and ENI resulted in an improvement in progression free survival (PFS) (the primary endpoint) compared to irradiation limited to the prostate bed. In addition, the majority of post hoc retrospective studies support ENI as does the pattern of failure following local treatment in high risk patients. In the absence of level one evidence to the contrary, patients at high risk for pelvic lymph node involvement should receive prophylactic ENI. With the completion of accrual to NRG/RTOG 0924 (n=2592, closed 7/2019) the impact of ENI on overall survival may finally be answered definitively, however, longer follow-up (5 to 10 years) is required. SP-0021 For the motion (for ENI) D. Böhmer 1 1 Charité Berlin Campus B. Franklin, Radioonkologie und Strahlentherapie, Berlin, Germany Abstract text Two Phase III trials are negative regarding ENI or show inconclusive results (RTOG 9413 and GETUG-01) ENI is associated with increased grade 3 GI-toxicity in a randomised trial (RTOG 9413) ENI in older randomised RTOG and EORTC-trials may represent an overtreatment Currently available data provide evidence for ENI in cN+ or pN+ patients The disadvantage for ENI when weighing survival benefit and treatment related toxicities is yet to be determined SP-0020 Against the motion (against ENI) A. Bossi Institut Gustave Roussy, Villejuif, France Abstract not received

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