ESTRO 2020 Abstract Book

S351 ESTRO 2020

most of the results were from observational studies and monocentric experiences. After the results of a recent randomized trial the International Guidelines on HCC have been updated and EBRT appears to have an expanding role in treating HCC, especially in case of lesions larger than 3 cm and with major vessels involvement. Several ongoing trials are investigating the potential benefits of EBRT and immuno therapy in combination. Modern radiation therapy modalities including particle therapy, with its known superiority in terms of biological effectiveness and physical selectivity, have certainly an emerging role in the management of HCC. Future clinical randomized trials are need to demonstrated the potentiality of such new technological advances. SP-0622 The medical oncologist's point of view J. Dekervel 1 1 UZ Leuven, Digestive Oncology, Leuven, Belgium Abstract text The development of new systemic treatments has revolutionized the landscape of advanced HCC. Recent phase III trials showed benefit of several new agents in first line (vs sorafenib) and second line (vs placebo). Systemic treatment of HCC is no longer a desperate choice after maximal exhaustion of locoregional approaches, but a valid option to consider at the MDT in all patients not candidate for treatments with curative intent. This lecture will cover when to consider systemic treatment options vs embolization techniques in intermediate stage HCC. Moreover, it is important to define embolization refractory HCC. The different systemic options available will be discussed, as well as a word on treatment sequencing. SP-0623 The interventional radiologist's point of view O. Van Delden Amsterdam UMC, Amsterdam, The Netherlands Abstract text Hepatocellular carcinoma (HCC) seems to become more important even in western countries. Main risk factors are liver cirrhosis of any etiology and chronic viral hepatitis. In recent years, rising incidences of non-alcoholic steatohepatitis (NASH)-related hepatocellular carcinoma have been reported. Surgical treatment options are liver transplantation and liver resection. The choice of treatment is related to the extension of the HCC and the quality of liver parenchyma. For HCC without liver cirrhosis liver resection is the treatment of choice. Noteworthy that NASH-livers are sometimes worse in the postoperative course than cirrhotic livers. Regarding liver cirrhosis as a precancerous lesion for HCC, liver transplantation is the optimal treatment for HCC in cirrhotic livers. However, it has been shown that oncological results are only acceptable if HCC meet MILAN criteria or slightly extended MILAN criteria as the University of California San Francisco (UCSF) criteria. The worldwide lack of organs for transplantation leads to the fact that liver resection is becoming more important in the treatment of HCC. Several classification systems and treatment algorithms Abstact not receievd SP-0624 The surgeon's point of view C. Riediger 1 , J. Weitz 1 1 University Hospital- University Of Dresden- Germany, Department Of Visceral- Thoracic And Vascular Surgery, Dresden, Germany

for HCC are available. Many of them as the Barcelona Clinic Liver Cancer (BCLC) classification from 1999 are old and nowadays not acceptable in its current form from a surgical point of view with an urgent need for revision. Staged hepatectomy and salvage liver transplantation in the setting of multimodal treatment are good options to treat primary or recurrent HCC. This talk will cover the controversy of resection versus ablation of hepatocellular carcinomas up to 3 cm as well as the treatment of hepatocellular carcinomas within and outside the Milan criteria with an analytic view on old treatment algorithms. Furthermore, the special aspect of liver surgery of NASH-related HCC will be discussed.

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