Abstract Book

ESTRO 37

S381

minor deviations concerned CTVp-breast (21.1%), level 1: CTVn-L1 (10.5%), and heart (9.9%). Among target volumes, CTVp_breast had the highest mean DI (0.80 +/-SD: 0.06) whereas level 2: CTVn-L2 had the lowest mean DI (0.50 +/-SD: 0.15). For OARs, heart had the highest mean DI (0.87+/-SD: 0.04) and brachial plexus the lowest 0.28(+/-SD: 0.08) together with left anterior descending coronary artery: A_LADcoronary (0.28 +/-SD: 0.12). Conclusion Online learning using FALCON-Educase for a dummy run is feasible and allows reducing the number of deviations, improving homogeneity in contouring and compliance to the guidelines in the frame of a dummy run. Further analysis of the contours from randomly selected patients in participating centers in HypoG-01 will allow for assessment of the sustainability of guidelines compliance. PO-0742 Intensity-modulated radiotherapy for the adjuvant treatment of breast cancer: a prospective study D. Pasquier 1 , F. Le Tinier 2 , A. Jouin 2 , S. Horn 2 , R. Boughzala 2 , A. Escande 2 , E. Tresch 3 , F. Crop 4 , X. Mirabel 2 , E. Lartigau 1 1 CENTRE OSCAR LAMBRET- CRISTAL UMR CNRS 9189- Lille University, Academic Department of Radiation Oncology, LILLE, France 2 CENTRE OSCAR LAMBRET, Academic Department of Radiation Oncology, Lille, France 3 CENTRE OSCAR LAMBRET, Department of Biostatistics, Lille, France 4 CENTRE OSCAR LAMBRET, Department of Medical Physics, Lille, France Purpose or Objective The aim of this study was to prospectively evaluate toxicity and quality of life (QoL) in a population of breast cancer patients treated by helical tomotherapy after breast surgery. Material and Methods This was a single centre, prospective study (NCT02281149). We included patients ≥ 18 years, with histologically proven breast cancer, undergoing adjuvant radiotherapy (RT) after partial or total mastectomy, with or without irradiation of lymph nodes. Prescribed dose to the breast/chest wall/lymph nodes was 50 Gy in 25 fractions of 2 Gy over five weeks with simultaneous integrated boost at surgical bed of 60 Gy in 25 fractions (25 fractions x 2.4 Gy). The primary endpoint was acute and long term (>90 days) toxicity related to RT, determined according to NCI-CTCAE v4.0. The associations between clinical and dosimetrical characteristics and toxicities were also analyzed. Variables at a p < 0.05 were considered to be significantly associated. Cumulative incidence of toxicity was estimated. Secondary endpoints was QoL evaluated by the QLQ-C30 and BR-23 questionnaires. Results We present an interim analysis of the first included patients. One hundred and fourteen patients were included between 18/11/2014 and 26/04/2016 with a median age of 56 years (range, 32–83). Median treatment time was 36 days (range, 21–44), and median follow up 13.1 months (range, 6.5-25.9) since the start of RT. Patients received irradiation of the breast (53.7%), of lymph nodes (93%) and 50.4% of them on the left side. The median dose delivered to the breast/chest wall/lymph nodes PTV was 50 Gy (range, 40.0 – 50.5) and a median boost to the surgical bed of 10 Gy (range, 9.6 – 15.0). Toxicities are presented in Table 1. Statistical multivariate analysis revealed a significant correlation between skin grade ≥2 acute toxicity and BMI (p = 0.003), skin D95% (p = 0.033) and subclavian skin D98% (p = 0.034). Grade ≥2 acute esophageal toxicity was

associated with the delivered dose to 7% to 36% of the esophageal volume (p<0.05). QoL questionnaires were completed by 84.3%, 86.8%, 79.6% and 73.9% of patients at baseline, 1-month, 6 months and 1 year, respectively. Global health status scores at 1, 6 and 12 months follow- up were significantly higher than those at inclusion, which means that patients experienced a better QoL. Score for breast symptoms at 1 month follow-up was significantly higher than at inclusion, reflecting a worsening of symptoms with respect to baseline. Scores at 6 months and 1 year were significantly lower than at 1 month, and did not differ significantly from score at inclusion.

Conclusion Breast adjuvant tomotherapy is well tolerated in patients needing a complex irradiation. Studies with longer follow-up are required to confirm these preliminary results and our study is ongoing. PO-0743 Assessment of heart substructures delineation in a phase III cardioprotection trial (SAFE2014) G. Francolini 1 , I. Desideri 2 , C. Becherini 2 , F. Terziani 2 , C. Delli Paoli 2 , E. Olmetto 2 , D. Pezzulla 2 , I. Meattini 2 , L. Livi 2 1 Azienda Ospedaliera Universitaria Careggi, radiotherapy, Firenze, Italy 2 University of Florence, Radiotherapy Unit, Florence, Italy Purpose or Objective Patients undergoing adjuvant radiotherapy for breast cancer have an increased risk of cardiovascular comorbidity, especially if left sided [Darby NEJM 2013]. However, no threshold dose have been evidenced in literature, and no data about heart substructures have been collected so far. In our institute, patients undergoing adjuvant treatment for breast cancer are included in a protocol to test a treatment strategy aimed to reduce cardiovascular morbidity (SAFE 2014, NCT2236806). This protocol is based on a periodic follow up with heart speckle tracking US, in order to detect preclinical heart damage [Meattini Med Oncol 2017]. In order to assess dose parameters and develop a dose constraint related to subclinical heart damage, a reliable and validated delineation of heart substructures based on a pre-existing guideline [Duane Radiother Oncol 2017] was made. Material and Methods Planning CT scan of 16 left sided breast patients included in SAFE protocol were imported on MIM® software version 6.6. Heart substructures were delineated by 5 different operators (CB,CDP,DP, EO and FT); Overall, 10 different heart substructures were delineated by each operator: