Abstract Book

S718

ESTRO 37

Purpose or Objective Studies have documented acute subclinical changes following radiotherapy (RT)[1, 2]. Acute changes in myocardial strain have been reported in the left ventricle(LV) globally following RT. More recently strain reduction within the LV apex has been shown to correlate with apical mean radiation dose. This study aims to document early subclinical LV myocardial dysfunction following breast RT at the segmental level and correlate this to RT dose Material and Methods Twenty-two patients (mean age 59 years (38-76)) underwent tangential breast RT. Deep Inspiration Breath Hold(DIBH) was not used. No patient received chemotherapy. Nineteen patients received 42.4Gy/16Fr to the entire breast, 3 patients received 50Gy/20Fr. Cardiac MRIs were performed immediately prior to, and 6-8 weeks following RT. Single breath-hold SSFP cine acquisitions were acquired in the cardiac imaging planes on a 3T Skyra MRI (Siemens). 2D strain maps in the cardiac short and long axis, 3D strain maps were generated through recombination of 2D maps. Using the AHA 17 segment model[3] (excluding segment 17 (apical cap)), segmental peak 2D/3D longitudinal, circumferential, and radial strain was measured with MRI tissue tracking software (cvi42, v4.5, Circle software). Corresponding RT doses to the AHA LV segments were determined from contours outlined in the cardiac axes in Oncentra Brachytherapy v4.5.2, before being imported into Mim v6.77(Mim Software) for dosimetric readout. Paired t-tests were performed between pre and post RT measurements for each segment, with a p<0.05 considered significant. Correlations between delta-strain values and radiation dose were performed, a p<0.05 being significant. Results The average mean heart dose was 2.39Gy (1.38-3.42). On average, 2D short axis circumferential strain was reduced in segments 1 (-23.57% vs -19.13% p=0.05) and 14 (- 23.50% vs -17.93% p=0.05). 3D circumferential strain was affected in segments 7 (-19.17% vs -16.39% p=0.02), 8 (- 20.67% vs -18.73% p=0.05) and 13(-18.48% vs-15.95% p=0.02). 3D radial strain was reduced in segments 8 (35.32% vs 25.46% p=0.02) and 9 (27.24% vs17.54% p=0.03). 3D longitudinal strain was reduced in segment 7 (-21.43% vs -19.12% p=0.03) only. There was a statistically significant negative correlation between dose and △ strain in segments 12 and 14 corresponding to mid anterolateral and apical septal walls. Statistically significant mixed negative and positive correlations between dose and △ strain were seen in segment 6 (basal anterolateral segment). Table 1 provides detailed segmental △ strain and dose correlations. A representative scatter plot of delta strain and dose is shown in Fig. 1. Conclusion Tangential left sided breast RT may result in early cardiac dysfunction. Preliminary analysis suggests a mixed but predominant negative correlation of LV segmental △ strain with dose following tangential radiotherapy, occurring predominantly in the anterolateral wall of the LV and apical septal segment. EP-1310 Breast irradiotion using three techniques: evaluate the dose distribution in internal mammary chain W. Wang 1 , L. Jianbin 1 , S. Yuanfang 1 , X. Min 1 , S. Qian 1 , Z. Yingjie 1 , L. Xijun 1 , L. Fengxiang 1 1 Shandong cancer hospital affiliated to Shandong University, Radiation Oncology, Jinan, China Purpose or Objective To evaluated the unplanned coverage dose to the internal mammary chain (IMC) in patient treated with radical

women compared to IBR- women. The potential confounding effects of tumour stage and treatment were controlled for. Follow-up was calculated from the date of mastectomy until the date of first recorded recurrence, death or end of study at 30 th of June 2016, whichever came first. For IBR+ patients, the implant was removed from the CTV in the radiotherapy planning images, and the target coverage (V 95%: CTV covered by > the 95% isodose) was compared between the IBR+ and the IBR- Median follow-up duration was 5.8 years (0.1-7.5 years). No statistically significantly differences were found in the incidence of recurrence rate ratios or in recurrence free survival (log-rank p = 0.142), OS (log-rank p = 0.096) or breast cancer specific survival (log-rank p = 0.147) between the IBR+ and IBR- groups. When removing the implant volume from the CTV it was evident that V 95% was slightly lower for IBR+ patients compared to IBR- patients: in the group of patients without lymph-node irradiation the means were 84% and 92%, respectively. groups. Results

Conclusion Implant based breast reconstruction before radiotherapy leads to a slight underdosage of the target, due to the build-up effect. However, no correlation with a higher incidence of recurrence or decreased OS was seen in IBR+ patients compared to IBR-patients. The recommendation to offer immediate breast reconstruction to breast cancer patients receiving mastectomy is safe according to the present analysis. EP-1309 Myocardial segmental strain changes detected with cardiac MRI following tangential breast radiation S. Tang 1,2,3 , E.S. Koh 1,2,3 , J. Otton 3,4 , R. Rai 1,2,3 , S. Ananthapadmanachan 4 , L. Holloway 2,5,6,7 , D. Tran 4 , G. Delaney 1,2,3 , L. Thomas 3,8 , B. Schmitt 9 , G. Liney 6,10 1 Ingham Institute for Applied Medical Research, Cancer Outcomes- Research & Evaluation, Liverpool, Australia 2 Liverpool Cancer Therapy Centre, Radiation Oncology, Liverpool, Australia 3 University of New South Wales, Faculty of Medicine, Sydney, Australia 4 Liverpool Hospital, Department of Cardiology, Sydney, Australia 5 University of Sydney, Faculty of Physics, Sydney, Australia 6 University of New South Wales, Faculty of Physics, Sydney, Australia 7 Ingham Institute for Applied Medical Research, Radiation Physics, Liverpool, Australia 8 University of Sydney, Faculty of Medicine, Sydney, Australia 9 Siemens Healthcare Pty Ltd, Research and Innovation, Sydney, Australia 10 Ingham Institute for Applied Medical Research, MRI Physics, Liverpool, Australia