ESTRO 36 Abstract Book

S637 ESTRO 36 2017 _______________________________________________________________________________________________

EP-1187 Heart dose evaluation in two free-breathing and deep-breathing modes of breast cancer patients R. Anbiae 1 , A.R. Taji 1 , A. Ahmari 1 , Z. Siavashpour 2 , M. Beigi 1 1 Shahid Beheshti Medical University, Radiation Oncology, Tehran, Iran Islamic Republic of 2 Shahid Beheshti University, Medical Radiation Engineering, Tehran, Iran Islamic Republic of Purpose or Objective To investigate how much respiratory manner of breast cancer patients during external beam radiotherapy would 21 patients with left breast cancer underwent CT simulation without contrast in one day and two positions; breath hold and free breathing, prospectively. Two CT image sets were imported to treatment planning system (Eclipse, version 6). Volumes of PTV (that included breast and chest wall), heart and ipsilateral lung in both image sets were contoured by an individual radiation oncologist. An experienced physicist designed the plans for both CTs. Prescribed dose was 50 Gy in 25 fractions for all included cases. Plans were then confirmed by the oncologist and heart and lung dose volume parameters were exported. Lung and heart Volumes, their V30 and V22.5 and also mean heart dose (MHD) in two condition were studied and analyzed. Results Mean age of patients was 46.9±12.1.Twelve patients had done MRM and 9 of them had done BCS. Mean heart volume, its V30, V22.5 and MHD in two breathing conditions, breath hold and free breathing, were 519±108 and 526±107 (P=0.545), 1.89±2.41 and 62.88±2.04 (P=0.030) , 2.41±2.68 and 4.35±3.42 (P=0.048) and 0.98±0.7 and 1.42±0.5 (P=0.002), respectively. Also left lung volume and V30 of lung in breath hold and free breathing modes were 1763±315 and 1114±219 (P<0.001) and 8.72±3.27 and 8.92±4.29 (P=0.819) respectively. Person correlation did not show linear relation between lung volume and its mentioned DVH parameters; for MHD obtained r=-0.421 (P=0.057), for heart V30 and V22.5 obtained r=-0.500 (P=0.021) and obtained r=-0.371 (P=0.097) and also, for heart volume r=0.032 (P=0.889). Conclusion All MHD and heart V30 and V22.5 variables were significantly higher with deep breathing in our study. It was shown that irritated heart volume was reduced significantly in this condition. V30 of lung were lower in deep breathing so deep breathing can be efficient method in left breath teletherapy. EP-1188 DIBH radiotherapy in left-sided breast cancer patients using an optical surface scanning system S. Schönecker 1 , M. Pazos 1 , P. Freislederer 1 , D. Reitz 1 , H. Scheithauer 1 , S. Corradini 1 , C. Belka 1 1 LMU University of Munich, Radiation Oncology, Munich, Germany Purpose or Objective There is a potential for adverse cardiovascular effects in long-term breast cancer survivors following adjuvant radiotherapy (RT). For this purpose, the deep inspiration breath-hold technique (DIBH) has been introduced into clinical practice, to maximally reduce the radiation dose to the heart. In the present study radiotherapy in DIBH was applied using the optical surface scanning system A total of 38 patients with left-sided breast cancer following breast conserving surgery were analysed. Normofractionated and hypofractionated radiotherapy protocols were eligible for this prospective clinical trial. Patient surface data and respiratory parameters were acquired using the laser surface scanner Sentinel TM (C-RAD affect their heart dose. Material and Methods Catalyst TM /Sentinel TM . Material and Methods

NSM (85.0% and 81.0%, respectively). They considered age, lymph node involvement, tumor size, extracapsular extension, involved surgical margins, lymphovascular invasion, triple negative receptor status and multicentric tumor as major risk factors. Considering tumor size, lymph node involvement and age as recurrence risk factors, the most-often suggested cut-off thresholds of those features were 5 cm, > 3 lymph nodes and 40 years old, respectively. Considering that after SSM and NSM, residual breast tissue can be left behind, the residual tissue considered as acceptable in the context of an oncologic surgery were 1 to 5 mm and 6 to 10 mm for 55% and 21% of the responders, respectively. There is no consensus for the necessity of evaluating residual breast tissue through breast imaging. Conclusion Although the indications of post- operative radiation therapy after SSM and NSM are not well defined, all standard relapse risk factors were considered as important, by surgeons, with regards to referring for post-operative radiation therapy. EP-1186 Real-time intrafraction motion in breast radiotherapy using an optical surface scanner D. Reitz 1 , S. Schönecker 1 , P. Freislederer 1 , M. Pazos 1 , M. Niyazi 1 , U. Ganswindt 1 , C. Belka 1 , S. Corradini 1 1 LMU University of Munich, Radiation Oncology, Munich, Germany Purpose or Objective Intrafraction motion is of special interest in modern breast cancer radiotherapy. Respiratory motion during intensity- modulated radiotherapy (IMRT) can cause problems in inadequate planning target margins or IMRT delivery. To date, only few data exist on real-time measured intrafraction motion in breast cancer patients. Continuous surface imaging using visible light offers the possibility to monitor patients’ movements in 3D-space without any additional radiation exposure. Material and Methods We observed thirty-one patients during 629 fractions that underwent postoperative radiotherapy following breast conserving surgery or mastectomy. During each treatment session the motion of the patient was continuously measured using the Catalyst TM optical surface scanner (C- RAD AB, Sweden) and compared to a reference scan taken at the beginning of each session. The Catalyst TM system works through an optical surface scanning with LED light (blue: λ = 450 nm) and reprojection captured by a CCD camera (green: λ = 528 nm; red: λ = 624 nm), which provide target position control during treatment delivery. For 3D surface reconstruction, the system uses a non-rigid body algorithm to calculate the distance between the surface and the isocenter and using the principle of optical triangulation. Three-dimensional deviations and relative position differences during the whole treatment fraction were calculated by the system and analyzed statistically. Results Overall, the magnitude of the deviation vector showed a mean change of 1.3 mm +/- 0.4 mm (standard deviation) and a median change of 1.1 mm during dose application (beam-on time only). Along the lateral and longitudinal axis changes were quite similar (0.9 mm +/- 0.3 mm vs. 0.9 mm +/- 0.5 mm), on the vertical axis the mean change was 1.1 mm +/- 0.3 mm. The mean net beam-on time of radiation therapy was 2.8 minutes. There was no linear correlation between the length of the fraction and the magnitude of deviation. Pearson’s correlation coefficient between mean time and mean magnitude of deviation vector over all patients was 0.25 (p-value= 0.175). Conclusion Mean real-time intrafraction motion was within two millimeters in all directions and is therefore of minor clinical relevance in postoperative radiotherapy of breast cancer.