ESTRO 2020 Abstract book

S383 ESTRO 2020

management are a multidisciplinary approach and a fast- track program for diagnosis and treatment. If promptly and adequately treated, patients with early stage disease have a good prognosis. Prospects of patients with advanced disease are still dismal but considerable hope exists that immunotherapy advances will synergize with radiotherapy to further enhance clinical outcomes. SP-0626 Surgery for NMSC C. Ulrich Leitung Hauttumorcentrum Charité (HTCC), Berlin, Germany SP-0627 Radiotherapy for non-melanoma skin cancer in 21st century A. Rembielak 1 , . 2 1 the Christie Hospital, Clinical Oncology, Manchester, United Kingdom ; 2 honorary Senior Lecturer, The University Of Manchester, Manchester, United Kingdom Abstract text The incidence of non-melanoma skin cancer (NMSC) is rapidly rising worldwide. Although mortality from NMSC is generally low, the total cost of treatment is becoming a considerable burden for health care services across the world due to the number of patients, aging population and increased complexity of cases which often require a specialist multidisciplinary approach. Radiotherapy has been used in NMSC for more than a century, in radical primary and nodal disease, in postoperative cases as well as in palliative settings. Recently there has been an increased interest in the use of skin radiotherapy in NMSC, not only in view of increased incidence and aging population but also due to an advantage that radiotherapy can offer to NMSC patients for organ and function preservation, particularly in cosmetically and functionally sensitive areas such as facial locations. In her talk Dr Agata Rembielak will discuss the current status and future perspectives of skin radiotherapy in 21 st century. SP-0628 What is our target after complex skin reconstruction? K. Skladowski Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Gliwice, Poland Abstract not received

Symposium: Novel approaches in the management of non-melanoma skin cancer

SP-0625 Merkel cell carcinoma: an oncologic emergency

J. Kaanders 1 , E.M. Zwijnenburg 1 , R.P. Takes 2 , W.L.J. Weijs 3 , J.E.M. Werner 4 , C.M.L. Van Herpen 5 , G.J. Adema 1 , S.F.K. Lubeek 6 1 umc St Radboud Nijmegen, Radiation Oncology, Nijmegen, The Netherlands ; 2 umc St Radboud Nijmegen, Otorhinolaryngology And Head And Neck Surgery, Nijmegen, The Netherlands ; 3 umc St Radboud Nijmegen, Oral And Maxillofacial Surgery, Nijmegen, The Netherlands ; 4 umc St Radboud Nijmegen, Surgery, Nijmegen, The Netherlands ; 5 umc St Radboud Nijmegen, Medical Oncology, Nijmegen, The Netherlands ; 6 umc St Radboud Nijmegen, Dermatology, Nijmegen, The Netherlands Abstract text Merkel cell carcinoma (MCC) is a rare and aggressive cutaneous malignancy of neuroendocrine origin. It has been associated with UV exposure, immunosuppression and infection by Merkel cell polyomavirus. The incidence of MCC is low, but there is an explosive rise in Western countries over the last decade. This is the result of an ageing population, more immunosuppressive medication and improved diagnostic recognition. Due to its rareness, health professionals often do not recognize MCC and are not always familiar with its aggressive biology. Expeditious diagnostic workup and prompt start of proper treatment in an expert cancer center is key to successful outcome. The general recommendation for localized disease is excision with generous margins. Postoperative radiotherapy is indicated in virtually all cases irrespective of resection margins. The motivation for radiotherapy is twofold: MCC tends to form cutaneous microsatellites and free margins do not necessarily indicate that all tumor is removed. Secondly, there is a high risk of (subclinical) lymph node metastases. The radiotherapy target volume should encompass the primary tumor site with wide margins as well as the draining lymph node stations. If possible, immunosuppressive medication should be discontinued or modified. Consequences of this should be weighed against the concern of more aggressive tumor behavior. Treatment for metastatic disease is palliative. MCC is a radiosensitive tumor and radiotherapy is very effective for symptomatic metastases. Various chemotherapy regimens have not been able to provide durable responses. However, a powerful new asset in the therapeutic armamentarium of MCC is immunotherapy. In the past two years the anti-PD- L1 antibody avelumab has been approved as a therapy for patients with metastatic MCC by various national and international regulatory bodies. The success of immunotherapy is an important landmark in the treatment of MCC. However, not all patients respond to immune checkpoint inhibition and further preclinical and translational research is required to optimize treatment strategies. The radioresponsiveness of MCC together with its immunogenic nature make this tumor an exquisite candidate for radio-immunotherapy. Preclinical models have indicated that radiotherapy is more effective with an intact adaptive immune system, and retrospective data suggest that local control after radiotherapy is diminished in immunocompromized patients. Conclusion All patients with MCC should be referred to an experienced team without delay. Prerequisites for proper

Abstract not received

Debate: This house believes that there is no future for adaptive radiotherapy in EBRT without an MR-linac

SP-0629 For the motion (there is no future for ART without an MR-linac) U . Oelfke Institute of Cancer Research, Belmont, United Kingdom

Abstract not received