ESTRO 2020 Abstract Book

S517 ESTRO 2020

sample size available and length of Tectum application. Further studies with 3 to 6 months extended therapy should be conducted to address this question. PO-0971 Factors predicting magnitude of heart dose reduction with DIBH-RT in left breast cancers R. Harjani Hinduja 1 , V. Kannan 1 , V. Anand 1 , R. Bajpai 1 , S. Deshpande 1 , S. Naidu 1 , K. Chauhan 1 , P. Umbarkar 1 , R. Kabre 1 , P. Alurkar 1 1 P D Hinduja National Hospital, Radiation Oncology, Mumbai, India Purpose or Objective Deep Inspiratory Breath Hold (DIBH) technique in Radiation therapy (RT) has significantly led to reduction in radiation doses received by the heart while treating left breast cancers. The purpose of this study was to identify physical parameters from the DIBH simulation CT scan that can predict the reduction in heart dose. Material and Methods This is a retrospective study of consecutive patients of left breast cancer treated with breast conservative surgery and adjuvant RT using DIBH technique between 1 st July 2018 and 31 st March 2019. Two simulation image sets, free breathing (FB) and DIBH, were available. Heart, left lung, Clinical Target Volume(CTV) and Planning Target Volume(PTV, PTV=CTV+5mm) were contoured on the free breathing scan. Three-dimensional Conformal Radiation Therapy (3DCRT) planning was done using tangents and subfields where necessary. The DIBH amplitude obtained during simulation, the diaphragmatic movement between the two simulation image sets and ratio of lung volume in DIBH scan over lung volume in FB scan were compared to the reduction in heart dose (mean heart dose and Volume receiving 30Gy-V30). An attempt was made to study the changes in the position and shape of the heart. Results Thirty-two patients treated for left breast cancer with DIBH radiation were eligible for the study. 30 of 32 patients had a reduction in the mean heart dose with DIBH technique. All patients had a reduction in V30, with 8 of 32(25%) having 100% reduction. The median reduction in the mean heart dose was 36% (6.4-71.2%) and in V30 was 90%. The median DIBH amplitude on simulation CT scan was 1.3cms (0.9-1.6cms). The median longitudinal diaphragmatic displacement between both image sets was 3.12cms (-0.2 to 6.5cms). The median of the ratio of Lung volume in DIBH images over FB images was 1.8 (1.51-2.52). Increase in ratio of lung volume in DIBH images over FB images correlated with reduction in mean heart dose (p- 0.018). There was no statistically significant correlation between DIBH amplitude or magnitude of diaphragmatic movement with reduction in mean heart dose. There was a trend noted between DIBH amplitude and reduction in V30 of heart (p-0.06). No correlation was noted between lung volume ratio or diaphragmatic movement with reduction in V30. When the heart shape was analysed, there was a significant change in the transverse diameter of the heart and it was consistently more elongated with an anterior and downward shift. Conclusion DIBH technique reduced the heart doses as compared to those on free breathing scan as reported in literature. We identified that lung volume expansion (given by ratio of lung volume in DIBH scan over FB scan) predicted reduction in mean heart dose and DIBH amplitude predicted reduction in V30. This study can be considered hypothesis generating to select patients who would benefit from DIBH treatment. PO-0972 Hypofractionation With Concomitant Boost In Breast Cancer: Efficacy And Toxicity. M.J. Garcia Anaya 1 , S. Segado Guillot 1 , Á. Fernández Forné 1 , C. Jódar Lopez 2 , I. García Ríos 1 1 Hospital Universitario Virgen de la Victoria, Radiation

Conclusion SBRT in breast cancer patients with extracranial OMD or OPD is well tolerated with excellent LC. The increase in utlization since 2017 points toward a growing acceptance of SBRT for OMD and OPD in breast cancer. The inferior, yet still acceptable local control rate of OPD patients, possibly reflects a different tumor biology. PO-0970 Tectum11 peptide in prevention and treatment of radiodermatitis in breast cancer E. Fernandez Lizarbe 1 , C. De la Pinta 1 , E. G. Arias- Salgado 2 , M. Martín 1 , T. Muñoz 1 , R. Hernanz 1 , V. Duque 1 , P. Barrionuevo 1 , S. Sancho 1 , R. Perona 2 1 University Hospital Ramon y Cajal, Department of Radiation Oncology, Madrid, Spain ; 2 Instituto de Investigaciones Biomedicas CSIC/UAM., CIBER de enfermedades raras. IDIPaz, Madrid, Spain Purpose or Objective To evaluate efficacy of Tectum11 peptide in prevention and treatment of radiodermatitis in breast cancer patients. Tectum11 activates telomerase activity, stabilizes and may rise the ability of the skin's stem cell to repair DNA damage decreasing apoptosis and minimizing fibrosis activation. Material and Methods This prospective, double-blind, randomized trial, compares basic moisturizing radiation cream with or without Tectum 11. Early stage breast cancer patients, receiving radiotherapy for the breast but not for the axilla, were eligible (15x267 cGy). Tumour bed boost if needed is performed either with brachytherapy (2x5Gy) or concomitant external beam radiotherapy (15x320 cGy). Randomly assignment 1:1 to moisturizing cream (Arm-A) vs Tectum 11 cream (Arm-B), from 1 week before to 1 week after radiation. Acute skin toxicity was evaluated using RTOG toxicity criteria in week 1,2,3 and 4, chronic skin toxicity was evaluated using RTOG for skin and subcutaneous tissue (subc) and Harris adapted scale in months 1, 6 and 12 after the complexion of treatment. For patients boosted with brachytherapy, during procedure at theatre under anaesthesia, a skin biopsy was taken to determine levels of DNA damage (% g-H2AX foci/cell) and fibrotic lesions ( % alphaSMAaSMA/dermis area). Results From 2014 to 2017, we included 68 patients with breast cancer meeting inclusion criteria.. 2 patients Arm-B excluded due to allergy reactions. Arm-A 34/ Arm-B 32. Acute toxicity: only ≤ grade II was reported, except 1 grade III toxicity in week 3 Arm-B. No statistically significant differences were found between Arm-A and Arm-B (p=0,89 week1; p=0,79 week2;p=0,64 week3; p= 0,42 week4). Chronic toxicity: majority of cases reported ≤ grade II, only 1 grade III subc RTOG toxicity at 6 and 12 months. . No statistically significant differences were found between Arm-A and Arm-B (p=0,59 skin, p= 0,45 subc, p=0,72 Harris month1; p=0.52 skin, p=0.37 subc, p=0,71 Harris month6; p=0,65 skin, p=0,73 subc, p=0,62 Harris month12).28 patients had tissue analysis (Arm-A 14/Arm-B 14). % cell with DNA damage: Low damage (≤5foci/cell) p=0.383, Intermediate damage (6-10foci/cell) p= 0,407 high damage (>10foci/cell) p= 0,265. % alphaSMA/dermis area showing myofibroblast presence: Mean Arm-A 0,93; Arm-B 0,64,p= 0.0253. There is a significant correlation between % area aalphaSMA/dermis and number of g-H2AX--foci/cell, p=0.0472. For this subgroup we did found statistically significant differences in skin, subc and Harris toxicity month1 (p=0,019; p=0.003;p=0.003) and skin toxicity Month 12 (p=0,024). Median follow-up 45 months, disease- free survival 98,5%, overall survival 98,5%. Conclusion Tectum11 decreases myofibroblast activation, correlated with lower DNA damage. We could not find clinicopathological correlation, probably due to the