ESTRO 2020 Abstract Book

S352 ESTRO 2020

SP-0630 Against the motion (there is a future for ART without an MR-linac) M. Scorsetti 1,2 1 humanitas Clinical And Research Hospital Irccs, Radiotherapy And Radiosurgery, Rozzano - Milan, Italy ; 2 humanitas University, Biomedical Science, Rozzano Milan, Italy Abstract text Adaptive radiation therapy (ART) is an evolving paradigm that could overcome some intrinsic limitations of current radiation therapy, i.e. the ongoing changes in the patient’s anatomy and physiology and in the tumor during the treatment course. Although the idea of adapting the treatment plan on daily modification has been debated for long time, some major obstacles have limited the clinical adoption of ART on a large scale. Most of available data derive from offline ART, mostly in the head and neck and thoracic cancers, and show small advantages, mainly from a dosimetric point of view with a still limited clinical impact. Having the possibility of an online treatment adaptation on a daily basis, MR-linac could fill the gap between the theoretical need for ART and its real life clinical implementation, without a significant impact on treatment times. However, I feel there are still a lot of gray zones that need to be clarified. First of all, the identification of patients who really deserve ART is still unclear. There are clinical situations in which no benefit can be expected adapting the treatment plan, like breast cancer or brain tumors. On the contrary, there are clinical scenarios, like prostate cancer, head and neck cancer or locally advanced lung cancer, in which we can expect dosimetric advantages and possibly clinical improvement with the adoption of ART. However, also in these cases, we are still missing data about the frequency of plan adaptation required to benefit the patients. Moreover, there are sites, like pancreatic cancer, liver tumors, upper and lower GI tumors, in which there are too few clinical data to support the implementation of ART on a large scale, although a theoretical benefit could be awaited. Beyond these uncertainties, I would like to highlight that the use of ART has been studied well before the introduction of MR-linac in the clinical arena. The real innovation coming with MR-systems could be the possibility to acquire images during the delivery but this is related to motion management and not to adaptive re-planning which is done “prior” to delivery. The two different concepts should not be mixed. Moreover, modern AI based systems might not require daily MR imaging and be able to extract the anatomy of the day from high quality CBCT and reference multimodality images. Quality of soft tissue resolution from diagnostic MR can be incorporated via AI into segmentation of daily CBCT. MR-linac will not be the only technology who will allow daily adaptation of treatment plan. Another issue is the real proportion of patients that could be treated with MR-linac, since patients with severe claustrophobia and contraindications to MRI cannot be considered for ART with this technology. However, they could be safely treated with other AI based systems, combined with more conventional Linacs. MRI guidance strategy for ART requires a radiation oncologist, medical physicist and radiation therapist to spend additional time at the machine, as tumor and normal organ changes are likely to be detected. Although rapid, adaptation of the treatment plan will require longer treatment times. During this treatment time, there may be an increase need to account for the movement of normal organs and comfort of the patients could become in issue. Due to all these reasons, I think that value of MR-

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 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-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-0626 Surgery for NMSC Presentation cancelled

SP-0628 What is our target after complex skin reconstruction?

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