Abstract book - ESTRO meets Asia

S123 ESTRO meets Asia 2018

Interdisciplinary: Professional education and training

Brdu assay and cell cycle were used to understand efficiency of nanoparticle in radiation therapy. Results TEM results revealed the size of AuN@SiO2 and AuS@SiO2 NPs with a mean diameter of approximately 23 and 31nm, respectively. The cells treated with AuN@SiO2 (amine) showed depletion of the cells in S phase (S=0%) in radiation groups, which emphasizes on higher potential of AuN@SiO2 (amine) for disturbance of cell cycle and induction of apoptosis. Brdu assay showed that MCF7 cells, containing nanoparticle have shown increased cell death up to 68% and 81% when irradiated by 6 and 18 MV radiation beam respectively. Conclusion Our result indicated that gold-silica shell-core nanoparticle can be applied in increasing the efficiency of radiotherapy and decreased its side effect. PO-298 Feasibility and Reliability of 2D-Shear Wave Elastography Imaging of Normal Thyroid Tissue R. Ahmad 1 , H. Abubakar Nattabi 1 , Y. Noorazrul 1 , M.S. Norhafidzah 1 , M. Mazlyfarina 1 , M.Z. Faizah 2 , N.Y. Ahmad Nazlim 1 1 Faculty of Allied Health Siences Universiti Kebangsaan Malaysia, Programme of Diagnostic Imaging and Radiotherapy, Kuala Lumpur, Malaysia 2 Faculty of Medicine- Universiti Kebangsaan Malaysia Me dical Centre., Department of Radiology, Kuala Lumpur, Malaysia Purpose or Objective To assess the feasibility and reliability of 2D-SWE acquisition of normal thyroid elasticity estimates at high level of precompression (LoP) relative to minimal LoP. Material and Methods 111 healthy volunteers with no history of thyroid disease were recruited. While in supine position with the neck extended, subjects were assessed for incidentalomas. Two raters independently acquired 2D-SWE elastograms of normal thyroid tissue at minimal and high levels of pre- compression (LoPs) and placed five 2mm sized regions of interest to obtain mean elasticity index estimates (E -mean ). Two successive acquisitions were made at both LoPs in the sagittal plane. Intraclass correlation coefficients (ICCs) were computed for assessment of absolute intrarater and interrater agreement. ICC values less than 0.5, 0.5-0.75, 0.75-0.9, and greater than 0.9 were indicative of poor, moderate, good and excellent reliability respectively. Bias was assessed on Bland Altman plots. Results The average E -mean and E -SD for normal thyroid tissue were 15.42±3.33kPa at minimal LoP and 68.71±15.34kPa at high LoP for all subjects. Average E -mean for the nodule-free thyroid gland was 14.89kPa at minimal LoP and 67.52kPa at high LoP. Incidental thyroid nodules were found in 37 participants. Their presence significantly increased E -mean (p=0.035; CI: 0.10-2.79) at minimal LoP but not at high LoP (p=0.360). Intrarater agreement was comparably good at both LoPs whereas interrater agreement was poor to 2D-SWE elasticity imaging of the normal thyroid is not adequately reliable at both high and low pre-compression levels. Caution should be exercised especially when interpreting elasticity indices from different observers and studies. Key words: Elasticity imaging techniques, Thyroid gland, Reproducibility of results. moderate. Conclusion

PO-299 Post-treatment ctDNA reflects residual disease for NSCLC patients receiving chemoradiotherapy J. Wang 1 , X. Lu 1 , L. Wang 1 1 Cancer Hospital- Chinese Academy of Medical Sciences, Radiation Oncology, Beijing, China Purpose or Objective The standard therapeutic modality for locally advanced NSCLC (LA-NSCLC) is definitive radiotherapy with concomitant chemotherapy. Residual disease after definitive therapy is responsible for tumor relapse, whereas traditional imaging assessment provides imperfect predictive ability. In this preliminary study, we aimed to explore the performance of ctDNA on the prediction of early progression for LA-NSCLC treated with chemoradiotherapy. Material and Methods LA-NSCLC patients who received concurrent chemoradiotherapy between 2013 and 2014, underwent prospective blood drawn prior to, during and post- radiotherapy in our center were screened for further selection. Favorable group included patients who achieved a time to progression > 24 months and still survived by December 31, 2016. Unfavorable group included those experiencing definite disease progression within 6 months after the commencement of initial treatment. With respect to ctDNA analysis, the capture probe was designed based on genomic regions selected with 1021 genes in total, which covers the most frequently mutated genes and exons in solid tumors. NGS sequencing was then performed for the SNVs detection. Results A total of 36 plasma samples from 12 patients were available and ultimately 31 samples were eligible for ctDNA detection and further analysis. Respective 6 patients were assigned to favorable and unfavorable groups, sharing comparable baseline clinical characteristics including age, gender, KPS, smoking status, comorbidities, pathological classification, TNM stage, staging method, therapeutic modality, radiotherapy technique, IGRT, RT dose, fractionation and EGFR mutation status. The median number of SNVs for individual sample was 7 (range: 0 - 29) and unfavorable group had more SNVs detection ( p = 0.076). The mean mutant allele fractions (MAFs) at pre-, during-, post- radiotherapy and pooled level integrating three time- points for favorable and unfavorable groups were 0.49 vs. 1.87 (p = 0.072), 0.41 vs. 0.56 (p = 0.561), 0.22 vs. 0.46 (p = 0.038) and 0.36 vs. 1.10 (p = 0.037), respectively. Due to the limited number of patients, no significant difference on ctDNA dynamics was observed. Contemporary measurements of circulating tumor markers including CEA, CA125, CYFRA21-1, SCC and NSE pre- and post-radiotherapy did not present difference between favorable and unfavorable group, neither did the dynamics of any tumor markers. Unfavorable group displayed numerically higher molecular tumor burden index (mTBI) than favorable group, though difference not reaching statistically significant level. Conclusion Pre- and post-therapy ctDNA evaluation may reflect the baseline tumor burden and residual disease, allowing for the identification of candidates at highest-risk of tumor progression suitable for consolidation therapy. PO-300 Study of 2 Brachy regime and response evaluation with PETCT Parameters in locally advanced CA Cervix N. Parihar 1 , M. Gupta 1 1 Indira Gandhi Medical college, Radiotherapy, Shimla, India