ESTRO 38 Abstract book

S716 ESTRO 38

epidemiological studies have shown cardiac morbidity and mortality as major complications of left-sided breast/chest wall irradiation Material and Methods In Academician F. Todua medical center, Research Institute of Clinical Medicine from October 2017 88 patients under 55 underwent radiation therapy to evaluate LAD and heart doses using DIBH (Deep Inspiration Breath- Hold) technique and FB (Free Breathing). Patients were divided in 3 groups: only breast, with regional LNs and with IM chain. Results Target Volume Coverage The target coverage was 97.0 ± 1.5% and 96.6 ± 1.2% (for V95) for the FB and DIBH plans, respectively. Other parameters HI and CI were also comparable. Ipsilateral Lung Doses The ipsilateral lung volumes were analyzed using 4 different dose volume parameters, i.e., V5, V20, V30, and Dmean. While DIBH increases volume of ipsilateral lung about 2 times, we did not found parameters V5, V20, V30 and Dmean appropriate for evaluation, although according to statistical parameters there was slight improvement in DIBH plans comparing with FB plans, but this was not considered comparable. Heart Doses It was observed, that V25 for the heart, one of the most useful parameter for heart dose evaluation, was almost near to zero in DIBH plans. Our statistical analysis showed that there was a significant reduction in dose to the heart in the DIBH plans for all other parameters too. Table 1 shows the heart dose observed from the FB and DIBH plans. LAD Doses It is known, that the doses received by the LAD are directly proportional to the risk of development of radiation-induced ischemic heart disease. We evaluated LAD doses in the FB and DIBH plans with 4 different dose volume parameters (V5, V10, V25, and Dmean). Table 2 shows the LAD dose observed from the FB and DIBH plans. Very few studies in the literature dealt with doses to the LAD and no standard protocols for the estimation of LAD doses and tolerances have been defined, so we present our statistical data just for comparison in dose difference, which is quite large in the value. For the first group (only breast or chest) the dose is almost negligible in DIBH plans, while for FB plans we have very high doses for all statistical parameters. Furthermore, in the FB plans, there was lot of fluctuation in doses to the LAD due to respiratory motion, which could be avoided in the DIBH plans.

Taipei, Taiwan ; 2 Taipei Medical University, School of Biomedical Engineering- College of Biomedical Engineering, Taipei, Taiwan ; 3 National Taipei University of Technology, Department of Electrical Engineering, Taipei, Taiwan ; 4 Taipei Medical University, Department of Radiology- School of Medicine- College of Medicine, Taipei, Taiwan ; 5 Taipei Medical University, Graduate Institute of Biomedical Materials and Tissue Engineering- College of Biomedical Engineering, Taipei, Taiwan Purpose or Objective Breast-conserving surgery followed by whole breast irradiation (WBI) is the standard treatment for patients with early-stage breast cancers. However, radiation dose to the heart and to the left anterior descending artery (LAD) during WBI is a risk factor of radiation-induced heart disease (RIHD). We developed PERSBRA (PERSonalized BReAst holder) technique to improve cardiac dosimetric profile during left sided WBI. PERSBRA involves a 3D- printed thermoplastic holder that adjusts breast position close to that could be achieved at the prone position. Previously we have reported a significant heart and lung dosimetric profile improvement with this technique. Here we further analyzed interfractional positional stability of the left breast. Material and Methods Fifteen participants with left-side early stage breast cancer were enrolled in our study. Lead markers were placed on participant’s left side, right side and anterior side. Three sets of CT simulation images were acquired in treatment positions (set 1: no PERSBRA; set 2: with PERSBRA; set 3: with PERSBRA and was acquired at 6th day after set 2). The difference of markers’ positions between the set 2 CT scans and the set 3 CT scans was recorded to evaluate the changes of breast position. The shape and volume changes were also evaluated from the contours on the set 2 CT scans and the set 3 CT scans. Target volumes and normal organs on all 3 sets were contoured by one radiation oncologist, and treatment plans were calculated with Pinnacle. Results With this device, the mean dose of heart and LAD in tangential fields was decreased by 28% (p<0.01) and 19% (p<0.05) respectively. The average errors of breast position with PERSBRA were 0.23±0.14, 0.54±0.15 and 0.67±0.16 cm in left-right(LR), craniocaudal (CC), and anteroposterior (AP) directions, respectively. The breast shape and volume difference between the set 2 CT and the set 3 CT was less than 1%. When applying set 2 CT- calculated treatment plans on set 3 CT, the PTV coverage (V 95% ) was 95.1±2.7 %, and D max was 109.4±0.5 %. Conclusion The radiation dose to the heart during left-sided WBI is a significant issue for early-stage breast cancer patients. Our analysis show that PERSBRA has good interfractional positional stability for breast immobilization and therefore supports its potential as a new option for cardiac sparing. EP-1309 Are OAR dose constraints for radical 3DCRT breast plans achievable? A one-year retrospective review. S. McCauley 1 , B. O'Connell 2 , C. Lyons 3 , R. Evans 3 1 Northern Ireland Cancer Centre, Clinical Oncology, Belfast, United Kingdom ; 2 North West Cancer Centre, Physics, Derry, United Kingdom ; 3 North West Cancer Centre, Clinical Oncology, Derry, United Kingdom Purpose or Objective Within our centre, a number of 3DCRT (3D Conformal Radiotherapy) breast cancer plans were exceeding mandatory dose constraints to achieve optimal 95% PTV (planning target volume) breast coverage. We performed a one-year retrospective review to ascertain our rate of non-conformity as well as identifying which treatment

Conclusion DIBH considerably reduced radiation doses to the heart, lung, and LAD artery without compromising target coverage. For our study patients, the probability of a major coronary event within 10 years will be significantly reduced. EP-1308 positional analysis of a personalized breast immobilization technique for whole breast irradiation T. Chen ,2 , M. Chung 3 , D. Tien 3 , R. Wang 1 , J. Chiou 1,4 , T. Kuo-Hsiung 3 , L. Long-Sheng 1,5 1 Taipei Medical University Hospital, Radiation Oncology,