ESTRO 37 Abstract book

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ESTRO 37

effective in lowering loco-regional recurrence rate regardless of molecular subtype. EP-1328 Impact of deep inspiration breath hold on heart and lung dose constraints in a large breast series G. Loganadane 1,2 , B.H. Kann 1 , M.R. Young 1 , C.A. Knowlton 1 , S.A. Higgins 1 , Y. Belkacemi 2 , L.D. Wilson 1 , M.S. Moran 1 1 Yale University School of Medicine, Department of Therapeutic Radiology, New Haven- Connecticut, USA 2 APHP. University of Paris-Est Creteil UPEC, Department of radiation oncology & Henri Mondor Breast Center, Créteil, France Purpose or Objective The purpose of this study was to evaluate the dosimetric impact of deep inspiration breath hold (DIBH) on the heart and the lungs in a large cohort of breast cancer (BC) patients Material and Methods This study included 360 patients undergoing three dimensional conformal (3D) tangential radiation using a field-in-field technique treated in our department between January 2015 and July 2017. Patients were divided into 3 cohorts for comparison: right-sided tumors (n=180), left tumors with DIBH (n=120) and left sided tumors with free breathing (FB) (n=60). The median values of various parameters were compared between groups (lung V20, lung V30, mean lung dose, heart V20, heart V30 and heart mean dose). For patients treated with hypofractionated radiation, we used V17, V28 and V38 instead of V20, V30 and V40 respectively to facilitate comparisons. Results There were significant differences in the 3 cardiac dosimetric parameters evaluated (V20, V40 and mean heart dose) in equivalent 2 Gy per fraction (EQD2), but differences in lung volume parameters were not significant. For left sided tumors, DIBH improved cardiac dosimetric constraints compared to FB: V17/V20 : 0.45% vs 1.6% (-71.9%) (p<0.0001), V38/V40: 0% vs 0.35% (-100%) (p=0.003) and mean heart dose (EQD2): 18Gy vs 26.4 Gy (-31.6%) (p<0.0001). Regarding the ipsilateral lung, the comparison of the 3 cohorts by the Kruskall-Wallis test (right sided tumors, left sided tumors with DIBH and left sided tumors with FB) did not show significant differences for any of the parameters: V17/V20: 16.6% vs 17% vs 18.6% (p=0,73), V28/V30: 13.7% vs 13.9% vs 14.9% (p=0.88) and the mean lung dose (EQD2): 9.7 Gy vs 9.6 Gy vs 10.6Gy (p=0,62). Conclusion This contemporary cohort study confirms that DIBH significantly reduced heart exposure in left sided breast cancer patients but does not appear to affect lung volume parameters in clinical practice. EP-1329 Clinical Outcomes Of Hypofractionated Vs Conventional Radiation In Women Treated For Breast Cancer A. Budrukkar 1 , N. Dash 1 , T. Wadasadawalla 1 , R. Jalali 1 , R. Upreti 2 , V. Parmar 3 , S. Gupta 4 , R. Badwe 3 , R. Sarin 1 1 Tata Memorial Hospital-, Department of Radiation Oncology - Tata Memorial Hospital, Mumbai, India 2 Tata Memorial Hospital, Department of Medical Physics, Mumbai, India 3 Tata Memorial Hospital, Department of Surgery, Mumbai, India 4 Tata Memorial Hospital, Department of Medical Oncology, Mumbai, India Purpose or Objective Hypofractionation for breast cancer has been proven be equivalent to conventional RT in various randomized trials. The aim of this study is to compare the two different fractionation regimens used in breast conserving

therapy (BCT) and mastectomy (MRM) over a period of 2 years- 2013 when conventional fractionation was used vs 2014 when hypofractionation was adopted in our institution. During this 2 year period 1288 women were treated with RT. Current data is an interim analysis of 520 women. Material and Methods Five hundred and twenty patients who were treated with radiation therapy from January 2013 (n=272) to December 2014 (n=248) with histologically proven invasive breast cancer were analyzed in this study. Patients were treated with conventional fractionation (early breast cancer:45Gy/25 fr, locally advanced: 50Gy/25 fractions) while MRM patients were treated to a dose of 45Gy/20 fractions. From January 2014 we adopted hypofractionation (40Gy/15 fractions) for both BCT and MRM. Boost was given to all patients undergoing BCT. Data was extracted from electronic medical records and radiation oncology information system. Data was entered using SPSS software for windows (v21). Survival analysis was done using Kaplan Meier test. Log rank test was used to compare various outcomes. Results Median follow up was 25 months. Three year the local control (LC) was 94.1% for the entire group, locoregional control (LRC) was 90.2%, disease free survival (DFS) was 76.5% and overall survival (OS) was 92.5%. In women undergoing BCT the 3 year LC in conventional and hypofractionated group was 97% and 97.6% (p=0.613), LRC was 94.9% and 95.6% (p= 0.894), DFS was 88.6 % and 90.4% (p=0.905), and OS was 97% and 98.1% (p=0.574) respectively. There was no difference in LRC in women undergoing BCT with conventional and hypofractionated radiotherapy even in presence of node positivity, presence of LVE, higher grade (IDC 3) and hormone receptor negative disease. In patients who underwent MRM the LC was 93% and 88.2% (p=0.077), LRC was 89.5% and 83.9% (p=0.017), DFS was 63.5% and 57.5% (p=0.8) and OS was 86.5% and 92% (p=0.476) in mild and moderate hypofractionation group respectively. At 3 year the LRC was 86.7% and 79.3% in node positive (p=0.018), 85.2% and 71.8% in hormone receptor negative (95% CI- 36.4-42.4, p=0.013), 87.6% and 78.6% (95% confidence interval [CI] 38.1-41.8, p=0.011) in IDC grade III tumor, and 85% and 63% in presence of LVE (p=0.113) in mild and moderate hypofractionation group respectively. Conclusion Clinical outcomes of hypofractionated RT were comparable to conventional RT in women undergoing BCT. However LRC rates were statistically inferior in patients undergoing MRM in presence of node positive disease, hormone receptor negative status and high grade (IDC grade 3) tumors. Hypofractionation should be cautiously used in this subgroup of patients. EP-1330 Dosimetric comparison of two techniques in left breast cancer with respiratory gating M. Valli 1 , I. Donegani 1 , E. Cekani 1 , D. Gaudino 2 , D. Daniele 1 , D. Bignasca 1 , A. Richetti 1 , S. Cima 1 , F. Martucci 1 , C. Azinwi 1 , G. Pesce 1 , D. Bosetti 1 , K. Yordanov 1 , I. Maddalena 1 , S. Presilla 2 1 Oncology Institute of Southern Switzerland, Department of Radiation Oncology, Bellinzona, Switzerland 2 Ente Ospedaliero Cantonale, Medical Physics Unit-, Bellinzona, Switzerland Purpose or Objective Aim of this study was to compare Volumetric multiple arcs therapy (VMAT) and 3D conformal radiotherapy (3DCRT) for sparing organs at risk (OAR) in left breast cancer patients treated with post-operative RT using Deep Inspiration Breath Hold (DIBH).