ESTRO 36 Abstract Book

S210 ESTRO 36 _______________________________________________________________________________________________

importance of this molecular biomarker is reflected in the updated WHO classification of central nervous system tumours that was published in 2016. Long term data from two large, randomised trials have shown that patients with 1p19q co-deleted anaplastic oligodendrogliomas derive significant survival benefit from the addition of chemotherapy to radiotherapy. More recent data from the NOA-04 study indicate that primary chemotherapy is not superior to primary radiotherapy in any molecular subgroup of anaplastic glioma and hence do not support the concept of ‘delayed radiotherapy’ in these patients. Despite the documented association of chemosensitivity with 1p19q co-deletion, a recent planned interim analysis of the CATNON study revealed that patients with anaplastic astrocytomas with inatct 1p19q chromosomal regions also derive significant benefit from the addition of adjuvant temozolomide to radiotherapy. It is not yet known whether the use of temozolomide concomitant with radiotherapy confers additional benefit; these hotly anticipated data are not expected to be available for at least two years. Hence, all patients with grade III gliomas appear to benefit from both chemotherapy and radiotherapy, with maximum survival benefit being achieved by ‘early’ rather than ‘delayed’ treatment. A number of questions remain, including the optimum scheduling of these treatments and the optimum radiotherapy regime for the different molecular subtypes. The question of radiation dose and volume is particularly important for this group of patients in whom long term survival can be anticipated and the risks and potential impact of neurotoxicity are significant. Strategies to reduce the long term neurocognitive impact of radiotherapy in these patients should be developed and incorporated into future clinical trials. SP-0392 ‘Paediatric’ brain tumours in adults C. Seidel 1 1 Universitätsklinikum Leipzig, Klinik für Radioonkologie und Strahlentherapie, Leipzig, Germany Paediatric brain tumours are rare in adults. Prospective trials are often lacking and treatment recommendations are essentially based on the experiences in children – although tumors in adults are different in many aspects. Efficacy and applicability of “paediatric” approaches in adult patients is therefore a matter of debate. Medulloblastoma (MB): MB is the most common brain tumor in children. It is relatively rare in adults, with an estimated incidence of 0.6 per million. MB in adults differ from the paediatric population in terms of location of tumor, histologic and molecular subtype and course of disease. In children MB frequently arise in the midline at the floor of the 4 th ventricle and vermis, whereas in adults the hemispheres are primarily involved. In children the majority of histological subtypes consist of the classical variant. In adults the desmoplastic variant is more frequently found. In adults late relapses are frequent. Like in children, surgery followed by radiotherapy is the standard of care. The addition of adjuvant chemotherapy confers a survival benefit according to a large retrospective analysis of American National database in more than 400 adult patients. After adjustment for relevant demographic and clinical factors, this study found that the addition of adjuvant chemotherapy to craniospinal irradiation was associated with superior overall survival for adult MB. In the recently closed German NOA-7 trial the addition of maintenance chemotherapy with 8 cycles cisplatin, vincristine and CCNU was investigated in a prospective, multicentric setting. Toxicity and survival profile of this study will be important for future treatment protocols. Novel stratifications of treatments in childhood MB are increasingly based on molecular genetic profiles. There have been clues over the past decade that adult MB is

biologically separate from childhood medulloblastoma. It has been shown that adult MB comprises 3 molecular variants rather than 4 and that the majority of tumors are SHH with smaller percentages comprising Wingless (WNT) and group 4. Moreover, several genomic studies have suggested that adult SHH MB is distinct from the pediatric entity, being enriched for PTCH1 and SMO mutations and coupled with a near absence of TP53 mutations. It can be expected that these information will in future gain an increasing importance for selecting adequately tailored treatment concepts for adult MB. Ependymoma (EP): Adult intracranial ependymoma are rare accounting for 2% to 5% of all intracranial malignancies. Decisive management principles were established accross the age groups, especially the attempt for radical resection. Postoperative local radiotherapy is the standard of care in children regardless of histological subtype. The role of adjuvant radiotherapy in the adult, however, is unclear and subject to controversies. The role of additional chemotherapy is unclear in children and adults. In children genetically distinct subgroups have been identified by genomic alteration in classic grade II and III ependymomas. They are supratentorial ependymomas with C11orf95-RELA fusion or YAP1 fusion, infratentorial ependymomas with high (type B) or low (type A) copy alteration number, and spinal cord ependymomas. Myxopapillary ependymomas and subependymomas have different biology and a better prognosis than ependymomas with typical WHO grade II or III histology. However, data for adults is scarce. Translation of molecular findings into clinical practice and adapted treatments is essential both for children and adults with the aim to improve tumour control and survival. Embryonal tumours (former stPNET): According to the new WHO classification of 2016 the former stPNET are now classified as embryonal tumours with distinct sub- classifications according to conventional histological description and the availability of molecular genetic profiles. Until today treatment concepts are still based on the traditional histological description both in children and adults. Embryonal tumours at supratentorial location are rare. Treatment concepts for these tumours both for children and adults are controversial. Surgery and craniospinal irradiation are still the corner stones in treatment management for both children and adults. The addition of chemotherapy is subject to prospective trials in children. With the introduction of the new classification and molecular genetic profiles adapted treatment concepts will evolve in future both for children and adults. Key points: Current concepts for paediatric CNS tumours in adults are based on experiences generated in paediatric neuro oncology. It is an open question whether these concepts prove to be as efficient and feasible. Late effects are known in children, but information is scarce for adults. There is a need for specifically tailored concepts in adults. SP-0393 Clinical opportunities with MR guided external beam RT S. Mook 1 1 UMC Utrecht, Department of Radiation Oncology, Utrecht, The Netherlands Nowadays, image guided radiotherapy is considered standard of care and is an integrated part of radiation treatment. Currently, cone beam computer tomography is the modality of choice for image guidance, however, limited soft tissue contrast and the absence of real time intrafraction imaging cause restrictions to its application. The superior soft tissue visualization of MRI was the incentive for the development of the MR linac system, Symposium: MR guided radiotherapy: the new standard of care in 10 years time