Abstract Book

S359

ESTRO 37

SP-0686 Against the motion J. Zindler 1 1 MAASTRO Clinic, Radiotherapie, Maastricht, The Netherlands Abstract text Stereotactic radiosurgery (SRS) is the preferred treatment for the majority of patients with a maximum of three brain metastases (BM). Recent technological advances with LINAC based SRS have enabled treatment of multiple BM (10 or more) within 20 minutes with comparable plan quality as Gamma Knife. These technological advances include fully automated single isocentre non-coplanar SRS using a frameless mask and a 6 degree of freedom correction couch. Recent studies have shown that survival is comparable after SRS for 2-4 BM versus 5 or more BM in patients with low volume BM. These studies raise the question if SRS is also the preferred treatment strategy for patients with 4 and more BM. Though, the previous mentioned studies are limited by selection bias and the main question if SRS provides clinical benefit over whole brain radiotherapy (WBRT) for the patient is not answered in these studies. In most guidelines in patients with 4 or more BM WBRT, primary systemtic therapy or best supportive care is adviced. Treatment choice depends on both patient as treatment characteristics. The potential advantages of SRS over WBRT are less hair loss, less neurocognitive damage, and a higher local tumor control probability of the BM. Potential disadvantages of SRS over WBRT are a risk of radionecrosis, a significant risk of 50-90% of new BM (distant brain recurrences or DBR) during follow-up, and higher costs. The risk of radionecrosis and DBR may impair quality of life and even survival. Moreover with Kaplan-Meyer analysis almost all patients will need WBRT during follow-up if they are initially treated with SRS and the initial number of BM is the most important prognostic factor of developing DBR during follow-up. Therefore it is likely that patients with 4 or more BM may benefit more from WBRT than patients with a limited number of BM. Though, it could be that a subgroup of patients with 4 or more BM may benefit of SRS over WBRT especially in the setting of effective systemic agents for BM. Before accepting SRS as the standard treatment for subgroups of patients with 4 or more BM, randomized phase III trials are needed. These randomized trials are currently ongoing, such as the NCT02353000. In this study the palliative value of WBRT is directly compared to the value of SRS in patients with 4-10 BM. In November 2017 22 patients were randomized and 9 centres were approved by the ethical committee for accrual in the Netherlands. The aim is to open more centres in the Netherlands and abroad to finish the trial within 2 years. Without level I evidence for the cost-effectivity of SRS over WBRT in patients with 4 or more BM and taking into account potential disadvantages of SRS, e.g. radionecrosis and high risk of DBR, WBRT or primary systemic therapy is still the preferred treatment in patients with 4 or more BM.

[5] Aoyama H. Jama 2006;295:2483–91. [6] Kocher M. J Clini Oncol 2011;29:134–41. [7] Sahgal A. Int J Radiat Oncol Biol Phys 2015;91:710– 7. [8] Mulvenna P. Lancet 2016;388:2004–14. [9] Yamamoto M. Lancet Oncol 2014;15:387–95. [10] Gondi V. Journal of Clinical Oncology 2014;32:3810–6. [11] Oehlke O. Strahlenther Onkol 2015;191:461–9. SP-0685 For the motion: A paradigm shift B. Baumert 1 1 Paracelsus-Klinik, Radiotherapy, Osnabrueck, Germany Abstract text The landscape in the treatment of brain metastases is changing. Numbers of patients with newly diagnosed brain metastases are increasing due to improved imaging and detection of brain metastases as well as prolonged survival due to advances in systemic treatment. More aggressive treatment concepts for patients with oligo- metastatic disease have been developed and curative indications increase. New systemic treatment possibilities like targeted therapies are available for brain metastases, partially with high response rates and thus making whole brain radiotherapy partially superfluous. Diagnosis and therapy concepts change and are increasingly based on molecular markers of the primary tumor. Some of the new targeted therapies are additive to radiation and could potentially further increase local control but also toxicity. Focal and precise modern radiation techniques have been established and have improved local control of brain metastases. A paradigm shift has taken place from whole brain radiation therapy (WBRT) towards local treatments like radiosurgery (SRS), stereotactic radiotherapy (SRT) or postoperative adjuvant radiation of the operation cavity. Randomized trials have shown efficacy of SRS/SRT alone to treat >= 5 metastases, large cohorts studies even for up to 10 brain metastases. With prolonged survival and increased tumor control questions of long term toxicity get increasingly important. Outcome towards quality-of-life and neurotoxicity need to be addressed. Recent studies investigate the possibilities of reduction of toxicities by radiation of the resection cavity only and have shown increased local control compared to operation alone. The use of SRS/SRT is another method to spare the hippocampus and therefore, avoid neurotoxicity. Focal radiotherapy avoids hair loss of the whole skull and thus increases quality-of-life. These facts and results can be weighed against the use of whole-brain radiotherapy (WBRT) in many settings especially in the light of randomized studies which have shown no increase in overall survival. Treatment strategies for patients with brain metastases are a multidisciplinary approach where patient selection and treatment selection are based not only on tumor load like number and size of metastases and patient-related prognostic factors, but also on biological tumor markers and available systemic or targeted therapy. Where an intracranial response maybe expected, no longer whole brain radiotherapy is necessary, but a focal radiation like SRS would be sufficient to control residual, new or progressive brain metastases in addition to the targeted therapy. Treatment of patients with brain metastases has developed into an individualized and tailored treatment strategy with an emphasis on high local control based on focal radiotherapy techniques.

Joint

Symposium:

ESTRO-EFOMP:

CBCT

in

radiotherapy: Improving and sharing best practice

SP-0687 CBCT in RT: Current status and standardising protocols M. Van Herk 1 1 Christie Hospital NHS, Divison of Molecular & Clinical Cancer Sciences, Manchester, United Kingdom Abstract text ‘ CBCT is the workhorse for image guided radiotherapy in most radiotherapy centres. However, there are concerns