ESTRO 36 Abstract Book

S626 ESTRO 36 _______________________________________________________________________________________________

4 Istituto Oncologico Veneto IRCCSS, Radiation Oncology Department, Padua, Italy 5 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Radiotherapy Unit, Campobasso, Italy 6 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Medical Physics Unit, Campobasso, Italy Purpose or Objective Single-dose intraoperative radiotherapy (IORT) is an alternative treatment for selected cases of early stage breast cancer. The purpose of this study is to present preliminary results of patients treated with IORT at Bellaria Hospital, Bologna, Italy Material and Methods We analysed data of 108 women who underwent lumpectomy and IORT with primary intent. IORT treatment was performed with a dedicated mobile electron accelerator (21 Gy were prescribed at 90% isodose). Data collected were histopathology, adjuvant treatment, clinical tolerability, local recurrences and outcomes. Results From December 2011 to December 2015, 108 women (median age 72 years) were treated with IORT. 75% of patients were treated with adjuvant ormonotherapy and 11.1% with combined chemotherapy plus hormonotherapy. The median follow-up was 26 months (range 2-52). 82.4% of patients had disease that was <2 cm in size, 65.7% of patients had an infiltrative duct carcinoma. At the end of follow-up 89.9% had a G0-G2 grade of late parenchymal fibrosis and 69.4% of patients a good cosmetic result. One patient underwent a mastectomy after five months because of chronic fistula in the irradiated area. One patient had a local relapse in a different quadrant and one patient had an axillary lymph node recurrence. Only one patient developed systemic metastasis. One patient died from breast progressive disease. Conclusion IORT represents a safe and effective alternative treatment option in selected patients with early breast cancer. Low complication rate with good clinical and cosmetic outcomes support IORT as a treatment option for selected women. EP-1153 Post-Mastectomy Hypofractionated Radiotherapy for Breast Cancer Treatment C.S. Ortiz Arce 1 , A. Chagoya González 2 , E.N. Barrientos Luna 2 1 Hospital Regional de Alta Especialidad Bajío, Radiotherapy, León, Mexico 2 Centro Médico Nacional Siglo XXI- IMSS, Radiotherapy, Mexico City, Mexico Purpose or Objective Radiotherapy (RT) for Breast Cancer improves local control and provides benefit in overall survival; this is given mainly in daily fractions (Fx) over a period of 5-6 weeks. Hypofractionated schedules reduce the number of sessions, shortening the treatment time. Many studies reported local recurrence in patients treated with breast-conserving surgery (BCS) with less than 5% in a lapse of 5 years. However, the indication of a hypofractionated scheme after a Modified Radical Mastectomy (MRM) is not clearly established, since there is only one study with a 7-year follow-up which reported 3 patients with local recurrence. Due to the high number of patients requiring RT, we initiated this transversal and comparative study, at the Centro Médico Nacional Siglo XXI, IMSS. We compared hypofractionated and conventional schedules in order to evaluate acute toxicity and local

EP-1151 Hypofractionated Radiotherapy in breast cancer treatment: A comparison between 3-DCRT and IMRT A. Fiorentino 1 , R. Mazzola 1 , N. Giaj Levra 1 , G. Sicignano 1 , G. Di Paola 1 , S. Naccarato 1 , S. Fersino 1 , U. Tebano 1 , F. Ricchetti 1 , R. Ruggieri 1 , F. Alongi 1 1 Sacro Cuore Don Calabria Hospital, Radiation Oncology Department, Negrar, Italy Purpose or Objective to compare 3-Dimensional Conformal RadioTherapy (3D- CRT) and 4-fields Intensity Modulated RadiationTherapy (IMRT) treatment plans, in terms of target dose coverage, integral dose and dose to Organs at risk (OARs) in early breast cancer (BC) hypofractionated RT. Material and Methods Twenty consecutive patients with early BC, after lumpectomy, were selected for the present analysis. A total dose of 40.5Gy in 15 fractions was prescribed to Planning Target Volume (PTV breast ) of the whole breast, while a simultaneous total dose of 48Gy was prescribed to the PTV of the surgical bed (PTV boost ). For each patient both a 3D-CRT plan with two couples of tangential-fields, and a 4-fields sliding-window IMRT plan were generated. Conformity and homogeneity indexes (CI, HI) were calculated for PTVs. For evaluation of OARs and normal tissue (NT), V 5Gy , V 10Gy and various organ specific V xGy values were analyzed. Results In terms of HI, IMRT (0.18 ± 0.02) was superior to 3D-CRT (0.23 ± 0.02) for the PTV breast (p<0.0001). Both techniques achieved the required dose for the PTV boost coverage, but a significant difference for CI was observed in favour of IMRT (0.9 ± 0.4) compared to 3D-CRT (3.7 ± 4.3) (p<0.0001). With regards to the heart, IMRT improved both mean and near-maximum doses. The inter-patients average of the heart D mean was (1.9 ± 1) Gy for 3D-CRT, and (1 ± 0.8) Gy for IMRT (p < 0.0001). For the analysis of left BC, the inter-patients average of the heart D mean was (2.9 ± 0.8) Gy for 3D-CRT, and (1.7 ± 0.6) Gy for IMRT (p = 0.0005). For the ipsilateral lung, the average of D mean for overall patients was 6.3 ± 1.4 Gy with 3D-CRT, and 4.8 ± 1.3 Gy with IMRT (p<0.0001). The V 25Gy value of the ipsilateral lung was also lower with the use of IMRT (p<0.0001). For the contralateral lung, the inter-patients median of D mean to the contralateral lung was 0.4Gy for 3D- CRT and 0.08Gy for IMRT (p<0.0001). For the contralateral breast, both D mean and D 2% were improved by the use of an IMRT planning technique. The inter-patients average of D mean was (0.3 ± 0.3) Gy for IMRT, while (1 ± 0.5) Gy for 3D- CRT (p <0.0001). For NT , all DVH parameters are in favor of IMRT, except the V 5Gy for which the difference was not statistically significant. The mean value of D mean was 2.2 ± 0.6 for 3D-CRT and 1.5 ± 0.4 for IMRT (p < 0.0001). Conclusion IMRT technique significantly reduced the dose to OARs and NT, with a better target coverage compared to 3D-CRT. Clinical evaluations are advocated. EP-1152 Intraoperative radiotherapy for early breast cancer: a monocentric experience A. Baldissera 1 , L. Giaccherini 2 , I. Marinelli 3 , A. Parisi 4 , G. Siepe 2 , O. Martelli 1 , F. Salvi 1 , D. Balestrini 1 , C. Degli Esposti 1 , I. Ammendolia 2 , G. Tolento 2 , V. Panni 2 , G. Macchia 5 , F. Deodato 5 , S. Cilla 6 , A.G. Morganti 2 , G.P. Frezza 1 1 Ospedale Bellaria, Radiotherapy Department, Bologna, Italy 2 University of Bologna, Radiation Oncology Center- Department of Experimental- Diagnostic and Specialty Medicine - DIMES, Bologna, Italy 3 Sapienza University, Radiation Oncology Department, Rome, Italy