ESTRO 2020 Abstract book

S549 ESTRO 2020

Conclusion According to our data, VMAT is a safe, effective and tolerable technique for the RT treatment of SBBC patients. Longer follow-up is needed to asses chronic toxicity. PO-0941 Deep inspiration breath-hold technique for the treatment of breast cancer: reduction of cardiac dose L. Montezuma 1 1 Hospital del Mar, Radiotherapy, Barcelona, Spain Purpose or Objective The purpose of this study was to evaluate the efficacy of voluntary deep inspiration breath-hold (DIBH) over the free breathing (FB) radiation therapy technique by comparing percent mean cardiac dose (Dmean) reduction. Also the correlation between cardiac contact distance (CCD) in both the axial (CCDax), parasagittal (CCDps) planes and Dmean was assessed. Material and Methods 20 patients with similar volume delimitation and 3D dosimetry treated using DIBH to a control group of FB. Dose volume were analyzed for V5, V20, V25, Dmean to the heart and left lung on FB and DIBH scans. We measured CCD in CCDax and CCDps planes, on FB and DIBH scans.

Conclusion Patients treated with DIBH we have found that, compared to FB patients, there is a large reduction in heart and lung doses. The technique is simple, well tolerated by patients and can be implemented for routine in radiation therapy of left sided breast cancer. PO-0942 Post-mastectomy radiotherapy after Immediate versus Two-Stage Breast Reconstruction. E. Bonzano 1 , M. Guenzi 2 , B. De La Lande 3 , E. Musat 3 , H. Albert-Dufrois 3 , J. Otz 3 , A. Clément-Zhao 3 , A.R. Filippi 4 , R. Corvò 2 , P. Poortmans 5 1 Fondazione IRCCS Policlinico San Matteo and PhD school in Experimental Medicine University of Pavia, Department of Radiation Oncology, Pavia, Italy ; 2 IRCCS Policlinico San Martino and University, Department of Radiation Oncology, Genova, Italy ; 3 Institut Curie Rene Huguenin Hospital, Radiotherapy Department, Saint Cloud, France ; 4 Fondazione IRCCS Policlinico San Matteo, Department of Radiation Oncology, Pavia, Italy ; 5 Institut Curie, Department of Radiation Oncology, Paris, France Purpose or Objective In patients undergoing implant-based reconstruction, PMRT could increase rates of infections, capsular contracture, implant loss, and overall reconstructive failure requiring revisional surgery. The association between PMRT and poor reconstructive outcomes is well documented. Immediate prosthetic breast reconstruction produces a satisfactory aesthetic result, with high levels of patient satisfaction. However, many patients are advised against immediate breast reconstruction because of concerns of implant loss and infection, particularly those requiring chemotherapy. Our study aimed to evaluate the patient's outcome according to two radiotherapy PMRT regimens, standard vs. hypofractionation, and two different types of reconstruction: tissue expander (TE) vs. immediate breast reconstruction(IBR). Material and Methods This study was conducted on 102 pts treated at 1 French and 1 Italian institute from April 2012 to June 2016. PMRT was delivered in two different regimes. The prescription dose to the PTV was 50 Gy/25 fr. 5 times per week and 46 Gy/20 fr., 4 times per week. Two-stage expander-implant reconstruction was performed in 53 patients, and the exchange is within 6 months since PMRT; IBR was perfomed in 49 pts. Results Outcomes data were recorded retrospectively. We compared the complication rate after PMRT with either TE or IBR. Outcome measures included a) occurrence of capsular contraction, evaluated by using the four-grade Baker scale, b) reconstructive failure (implant loss), and C) aesthetic results. We recorded minor complications in 5 (9.26%) TE patients and 3 (6.12%) in IBR patients. Among

Results Dose to heart and left lung was significantly lower in DIBH plans than in FB by all metrics. When DIBH was compared with FB, Dmean for heart was 0.91 vs 2.37 Gy (p<0,001). Overall, DIBH reduced Dmean to the cardiac structures by 46,56% compared with FB. Equally significant were differences in V5, V20, V25 for all cardiac and Lung structures. When was compared percent Dmean reduction between CCD in both the CCDax and CCDps planes on FB and DIBH, using the Spearman’s rank coefficient, there was no correlation between those variables (p>0,05) in both cases.