ESTRO 38 Abstract book

S138 ESTRO 38

Short duration (<25 days) treatment schedules with a higher radiation dose were associated with higher EoRT lymphocyte counts, an observation consistent with published models indicating less radiation dose of circulating blood by an approach of radiotherapy using fewer fractions. Radiation to multiple sites and concomitant chemotherapy conversely independently lowered EoRT lymphocyte count. Radiation-induced lymphopenia was associated with increased risk of acquiring a subsequent infection and mortality.

Japan; 3 Tokyo Bay Advanced Imaging and Radiation Oncolgy Clinic Makuhari, Radiation Oncology, Chiba, Japan ; 4 Chiba Cancer Center, Surgical Pathology, Chiba, Japan Purpose or Objective Hypofractionated high-dose IMRT had improved the local control of glioblastomas (GBMs), but still had higher risk of radiation injury even with tailor-made setting of radiation doses owing to the methylation status of MGMT gene promoter. We investigated the effect of bevacizumab (BEV) on control of the tumor and prevention of radiation injury after hypofractionated tailor-made IMRT. Material and Methods Newly diagnosed GBMs were enrolled. Residual enhanced lesions plus surgical cavity were defined as GTV, and 3- layered CTVs were contoured surrounding the GTV: CTV1=GTV+3mm, CTV2=GTV+18mm, and CTV3 was high- intensity volume on FLAIR images. PTV1, PTV2 and PTV3 were defined by expanding CTVs with 2mm margin. Prescribed doses for PTV2 and PTV3 were unified as 40Gy and 32Gy, but the dose for PTV1 was settled as 48Gy for MGMT methylated (Met) but 68Gy for unmethylated (UnMet) cases. IMRT was initiated 5 weeks after craniotomy, and the above doses were delivered with IMRT technique by 8 fractions. BEV was administrated 3 weeks after craniotomy (2 weeks prior to IMRT), and continued bi-weekly for 6 cycles. Temozolomide (TMZ) was also initiated 3 weeks after craniotomy and administrated for 42 days. Adjuvant BEV/TMZ was administrated every 4 weeks for 12 cycles or until tumor progression. The primary endpoint was overall survival (OS), and secondary endpoints were progression-free survival (PFS), radiation necrosis-free survival (RNfS), and qualitative survival (QS) which was defined as the time to KPS<70%. The outcome of patients was compared with historical control of 76 patients with GBM treated by tailor-made IMRT without BEV. Results 25 GBMs, 10 Met and 15 UnMet cases, were enrolled. The PFS of patients treated with BEV (median: 19.2m, 95%CI; 13.3m- not reached) was longer than that without BEV (9.7m, 7.8-16.3m), although this difference was not significant ( P =0.140). BEV improved the 6-months and 12- months RNfS rates from 83.0% to 98.8% and 58.5% to 72.6%. However, this difference disappeared after completion of the protocol treatment, and 18-months RNfS rates in BEV group (35.8m) was similar to that in historical group (40.9%). BEV significantly prolonged the median QS (13.8m vs. 19.0m, P=0.037), but did not improved the OS of patients (not reached vs. 21.2m, P =0.657). Conclusion BEV showed effect on prevention of radiation injury after hypofractionated IMRT, but this effect discontinued after withdrawal of this agent. Concurrent use of BEV had contributed to keep patients’ performance status, but showed only limited efficacy on tumor control. OC-0280 ReRT with bevacizumab is related to lower rate of radionecrosis as reRT alone for recurrent glioma D. Fleischmann 1 , J. Jenn 1 , S. Corradini 1 , V. Ruf 2 , R. Forbrig 3 , M. Unterrainer 4 , N. Thon 5 , F.W. Kreth 5 , C. Belka 1 , M. Niyazi 1 1 University Hospital- LMU Munich, Department of Radiation Oncology, Munich, Germany; 2 Faculty of Medicine- LMU Munich, Institute of Neuropathology, Munich, Germany; 3 University Hospital- LMU Munich, Institute of Neuroradiology, Munich, Germany; 4 University Hospital- LMU Munich, Department of Nuclear Medicine, Munich, Germany; 5 University Hospital- LMU Munich, Department of Neurosurgery, Munich, Germany

OC-0279 Concurrent and adjuvant effect of bevacizumab on hypofractionated tailor-made IMRT for glioblastomas T. Iuchi 1 , R. Hara 2 , K. Hatano 3 , T. Sugiyama 4 , G. Togasaki 2 , T. Setoguchi 1 , Y. Hasegawa 1 , M. Itami 4 , T. Sakaida 1 1 Chiba Cancer Center, Neurological Surgery, Chiba, Japan; 2 Chiba Cancer Center, Radiation Oncology, Chiba,