ESTRO 38 Abstract book

S360 ESTRO 38

introduction of potent TKI drugs targeting specific driver mutations with significant CNS efficacy. The role of immunotherapy in treating BM is less clear, but initial reports tend to challenge upfront local brain directed treatment as well. Regardless of the recent advances CNS failure remains a significant challenge in these patients and there is a clear need to precisely define the role and optimal timing of local therapies. This will be critically reviewed in the context of BM from NSCLC as we. Finally, a quick look to BM from melanoma and breast cancer will reveal similarities and differences in the management of BM compared to NSCLC. SP-0696 Integration of surgery and radiosurgery S. Blamek 1 1 Maria Sklodowska-Curie Institute and Cancer Center- Gliwice Branch, Department of Radiotherapy, Gliwice, Poland Abstract text The results of recently published randomized clinical trials indicate that radiosurgery should be preferred over whole brain radiotherapy (WBRT) in patients with resected brain metastases. Along with the results of the studies showing the advantages of SRS as opposed to WBRT in patients with intact metastases, they put radiosurgery in the position of the first choice treatment in patients metastatic disease in the brain. Nevertheless, there is still a number of patients who will benefit from neurosurgical resection of the metastatic tumor. Patients with large lesions, tumors with cystic component, presenting symptoms of mass effect and compression of neural structures are pointed out as potential candidates for surgery. On the other hand, there is emerging evidence that good outcome in patients with large metastases treated with hypofractionated radiosurgery can be achieved even in patients harboring tumours exceeding 4 cm in diameter. It is now commonly accepted that the limiting factor for the use of radiosurgery is not the number of metastases but rather the total volume of the tumours in the brain. It is true for single fraction treatment but in case of fractionated treatment the total volume of the neoplasm may play less important role. Consequently, the indications for surgical treatment in case of single and multiple metastases both in the setting of primary management and salvage after treatment failure are evolving. There is also much controversy about target definition for radiosurgery in case of postoperative treatment. Cavity shape and volume change over time which makes timing of postoperative radiosurgery one of the factors influencing outcome. Alternatively, preoperative radiosurgery emerges as a solution, potentially allowing for combination of benefits of surgery and radiosurgery without jeopardizing outcome, especially in the context of postulated association between surgical procedure and the risk of leptomeningeal disease. Finally, the issue of differentiation between radiation necrosis and tumour progression is gaining importance. The patients are followed up with MRI after the initial treatment which allows for detection of tumor volume increase far before clinical symptoms become apparent. It results with more effective salvage treatment but at the same time the risk of unnecessary intervention is increased and the first choice salvage treatment less obvious.

without hippocampal avoidance on memory performance of patients treated for brain metastases. On a second level, structural and functional changes of the brain will be investigated which underly the neurocognitive side- effects of both treatments applying state-of-the-art neuroimaging techniques. It is hypothesized that the novel, recently established technique of WBRT with dose escalation to brain metastases and hippocampal avoidance minimizes the side-effect of cognitive deterioration while at the same time providing an optimal treatment for brain metastases. SP-0694 Radiosurgery alone in multiple brain metastases J. Zindler 1 1 Erasmus MC, Radiotherapy, Rotterdam, The Netherlands Abstract text Stereotactic radiosurgery (SRS) alone is a promising treatment strategy in the multimodality treatment of brain metastases (BM). Especially in low volume BM high local control rates can be achieved. Compared to whole brain radiotherapy (WBRT) it is assumed that the risk of side effects such as alopecia, fatigue, and neurocognitive damage is less and thereby quality of life is better preserved. Disadvantages of radiosurgery alone is the relatively high risk of development of new brain metastases during follow-up and a risk of symptomatic radionecrosis, especially in high volume BM. These disadvantage may impair quality of life of the patient. In the setting of more than 3 BM there is no level I evidence for the use of SRS in both low as high volume BM. Also for the use of WBRT, there is a general lack of level I evidence, especially since the publication of the QUARTZ trial in the primary setting (Mulvenna 2016), but also after the EORTC-trial (Kocher 2011/Solfietti 2013) in the elective setting. Nowadays SRS is generally accepted as a treatment option for patients with a maximum of 3 BM. The main question is if SRS preserves better quality of life than WBRT in the setting of more than 3 BM, taking into account both the advantages as the disadvantages of SRS. This question is addressed in the Dutch NCT02353000 trial (Zindler 2017). Another potential value of SRS in the setting of a multimodality treatment with immunotherapy (Schoenfeld 2015) is the induction of a so called abscopal effect. Also upfront SRS in the setting of targeted agents is a promising treatment strategy to enhance penetration of the blood-brain barrier (Magnuson 2017). In conlusion, SRS is a promising treatment strategy for patients with more than 3 BM, but also in a multimodality approach with immunotherapy and targeted agents. In a rapidly changing field with more and more systemic treatment options, both the use of SRS as WBRT needs to be redefined in the setting of BM. SP-0695 Systemic treatment as alternative or addition to radiotherapy Nicolaus 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. Radiotherapy has been the mainstay of treatment and cytotoxic systemic therapy was not considered a viable option as sole treatment strategy. Still in recent years, complex 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. As a prime example, management of NSCLC patients with brain metastases has changed significantly since the

Symposium: Improving delineation in RT: not only for the doctor

SP-0697 How to handle clinical inter-observer variation in contouring assessment M. Gooding 1