ESTRO 38 Abstract book

S679 ESTRO 38

macroscopically radical resection while 16 (35,5%) received a partial resection. The remaining 12, deemed as non-surgical patients, had just a neuroradiological diagnosis of GBM in 10 cases, while 2 of them (4,4%) were biopsied. MGMT promoter was methylated in 33,3% (15/35 patients) of the surgical cohort. IDH-1 mutation was reported in just 1 patient (1/35, 2,2%). Oral temozolomide (TMZ) was given, either in the concomitant or in the adjuvant setting, to 15 (34,9%) and to 20 patients (50%) respectively. Overall survival (OS) was estimated since the last day of HFRT. Results All patients completed the prescribed RT course of 42 Gy in 14 daily fractions (3 Gy/die), except one (2,2%) that was stopped at a total dose of 36 Gy, due to the worsening of neurological conditions. Median OS was only 6 months for the overall population. We observed that baseline (Bs) KPS was related to OS; in fact, patients with KPS >70 had a longer median survival time (7 vs 5 months, p 0.031) compared to patients with KPS ≤70. MGMT promoter methylation is related with a marginal OS benefit (median OS 9 vs 4 months, p 0.079) (Fig1).

At the multivariate analysis (MVA) administration of adjuvant CT was the only variable related to a better survival (p 0.04; HR 0,268, CI 0,074-0,964), while KPS>70 post HFRT conferred a marginal survival benefit (p 0.06; HR 0,125, CI 0,014-1,103). Conclusion In the management of very elderly GBM patients, HFRT 3D- CRT, eventually combined with concurrent or adjuvant TMZ, appears to be a feasible and beneficial therapeutic option in patients with favorable features, such as good Bs KPS and MGMT promoter methylation. On the other hand, We suggest an accurate clinical and radiological multidisciplinary evaluation for patients at poorer prognosis (baseline KPS 60-70 and un-methylated MGMT promoter), in order to select the best treatment option (HFRT vs best supportive care) on a case by case strategy definition. EP-1233 Stereotactic radiosurgery to brain metastases using Varian HyperArc in the Beatson Cancer Centre O. Kjartansdottir 1 , A. Williamson 2 , A. Patibandla 1 , S. Currie 3 , R. Carruthers 4 , A. Chalmers 4 , A. James 1 , S. Nowicki 1 1 Beatson West of Scotland Cancer Centre, Clinical Oncology, Glasgow, United Kingdom ; 2 Beatson West of Scotland Cancer Centre, Radiotherapy, Glasgow, United Kingdom ; 3 Beatson West of Scotland Cancer Centre, Physics, Glasgow, United Kingdom ; 4 Institute of Cancers Sciences- University of Glasgow, Clinical Oncology, Glasgow, United Kingdom Purpose or Objective Stereotactic radiosurgery (SRS) has been established as an effective way of treating patients with metastases, delivering high doses to target lesions whilst sparing normal tissues in a highly conformal way. The Varian HyperArc VMAT treatment planning system utilizes several specialized functions to optimize a treatment plan, including 5 non-coplanar hemi-arc beam arrangements, automated settings for isocentre location and collimator angles, aiming to further increase conformity of target dose while reducing doses to surrounding normal tissues. HyperArc became available for clinical use in the Beatson Cancer Centre in October 2017. Prior to this we had already moved from a multi- to a single-isocentre

Moreover, we observed that post-HFRT KPS>70 (p 0.004), discontinuation of the steroid therapy (p 0.024) and administration of concurrent (p 0.030) or adjuvant CT (p 0.01) were related to a better OS (Fig2).