Abstract book - ESTRO meets Asia

S68 ESTRO meets Asia 2018

Results Over a 12-months period, 21 patients of high-grade glioma were treated (male to female ratio 2:1). Most of the patients had GBM (n=17) while the others had anaplastic oligodendroglioma and anaplastic astrocytoma. 8-patients had their MGMT-methylation status known (5 positive, 3 negative). Approximately 40% of the patients had their surgery in a high-volume center, and 15 patients had complete resection of their tumour while the others had debulking surgery. All patients were treated with standard adjuvant STUPP protocol with radiotherapy and Temozolamide. Median survival was 13 months which is comparable to the published data. Six patients are still alive out of 21 patients. Unifocal disease exhibited better outcome than multifocality, although the numbers were too small to draw any meaningful conclusion. Conclusion GBM confers a poor prognosis. Surgical resection followed by adjuvant chemo-RT as per the STUPP protocol remains the standard of care. Despite the lack of routine biomarker testing in Bangladesh, our outcome data is similar and in line with data from other high-volume centers. Key words: Glioblastoma multiforme, radiotherapy, concurrent Temozolamide. PO-168 Moderate hypofractionated accelerated radiotherapy using tomotherapy for patients with glioblastoma Y.I. Kim 1 , C. Moon-june 1 , K. Jun-Sang 1 , K. Ki-Hwan 1 , K. Jin-E 1 1 Chungnam National University Hospital, Radiation Oncology, DaeJeon, Korea Republic of Purpose or Objective The outcome for patients with Glioblastoma (GM) still remains poor (median survival 16 months and overall survival rates 27% at 2 years). Local progression is common after radiation therapy with or without chemotherapy for GM. So, hypothesizing that a hypofractionated accelerated radiotherapy to the gross tumor volume (GTV) might increase local control of GM. We investigated whether hypofractionated accelerated radiotherapy improved local control in patients with GM. Material and Methods Sixteen patients with GM were treated with radiotherapy using tomotherapy. All patients were Karnofsky performance status (KPS) > 60 with a histologically proven GM by operation. All patients were treated by radiotherapy using tomotherapy within 4-6 weeks after operation. Clinical target volume (CTV) contains the GTV, plus a margin 2cm which is determined to consider the anatomic structure. Planning target volume (PTV) margin is 2mm all direction from GTV or CTV. A dose 6100-6750 cGy was delivered in 28-30 fractions, fraction size 210-230 cGy to GTV. Critical structures including the optic chiasm/nerve and brain stem were limited to 4000 cGy. Results Median follow up for patients was 16.1 months. Only one patient did not complete full dose radiotherapy due to tumor progression. Median OS was 12.9 months (1.9-41.9, and 2 years OS was 43.3 %). Median progression free survival (PFS) was 8.9 months (1.1-41.9, and 2 years PFS was 26.7 %) retrospectively. No grade 4 and 5 toxicity. Conclusion There was no difference OS and PFS in using moderate hypofractionated accelerated radiotherapy compared with historical reports. More study is needed to improved treatment outcomes for patients with GM.

PO-169 Comparative Dosimetric Evaluation of 3D-CRT Versus VMAT For Postoperative Pituitary Adenoma S.S. Nanda 1 , M. Rastogi 1 , A.K. Gandhi 1 , K. Sahni 1 , R. Khurana 1 , R. Hadi 1 , S.P. Mishra 1 , A. Srivastava 1 , H.B. Singh 1 , S. Rath 1 , P.C. Rai 1 , M.L.B. Bhatt 2 1 Dr Ram Manohar Lohia Institute of Medical sciences, Radiation Oncology, Lucknow, India 2 King George Medical University, Radiation Oncology, Lucknow, India Purpose or Objective Radiotherapy (RT) is usually delivered to symptomatic patients after surgery in pituitary adenomas. Pituitary irradiation has undergone a spectral change from the traditional 3-dimensional conformal radiotherapy (3D- CRT) to stereotactic radiotherapy. Volumetric modulated arc therapy (VMAT) can provide better coverage of target volumes and sparing of organs at risk (OARs). We intended to compare dosimetric aspects of 3D-CRT vis a vis VMAT in pituitary adenoma. Material and Methods The study was a prospective observational study. Computed tomographic simulation data of 10 patients of postoperative symptomatic pituitary adenomas fused with post-operative magnetic resonance imaging data and treated with 3D-CRT, were used for dosimetric comparison with subsequently generated VMAT plans. The postoperative residual tumor and tumor bed were included in clinical target volume (CTV) with 5 mm uniform expansion to form planning target volume (PTV). 3DCRT was planned using 3 field technique on Xio while VMAT was planned using Monaco version 5.0. The patients were treated with 3D-CRT plan while the VMAT plans were used to compare the dosimetric aspects of the treatment. A dose of 50 Gy in 25 # @ 2 Gy / # was delivered over 5 weeks to PTV. The PTV indices analyzed were D mean, D2 (dose received by the hottest 2 percent volume), D98 (dose received by 98%), homogeneity index HI [(D2- D98)/D50)] and conformity index CI (PTV volume/volume of PTV covered by 95% isodose). Dmax and D2 (dose received by hottest 2cc) for the brain stem, both optic nerves, optic chiasma and both temporal lobes were evaluated. Planning objective was to cover > 95% of PTV with 95% of the prescription dose. SPSS (version 20.0) was used for statistical analysis with p <0.05 considered significant. Results Median age was 52 years with predominant (70%) being macro adenoma. 9/10 patients had functional tumor with endocrine dysfunction. Mean PTV volume was 30.4 cc. Mean biologically effective dose for 3D-CRT vs. VMAT were 60.2 Gy vs. 61.1 Gy (95%CI -3.07 to 2.08; p=0.60). Mean treatment time was 12 minutes in 3D-CRT vs 8.8 minutes in VMAT, p= 0.03. Mean monitor units (MU) delivered were higher in VMAT compared to 3D-CRT 320 ± 12 vs 292 ±15, p=0.0002. A comparative analysis of PTV and OAR parameters for 3D-CRT vs VMAT has been enunciated in table 1.

Conclusion VMAT was found to be superior to 3D-CRT dosimetrically in terms of higher conformity, sparring of the brainstem and temporal lobe and smaller treatment time but at the cost of higher MUs being delivered.