ESTRO 36 Abstract Book

S634 ESTRO 36 2017 _______________________________________________________________________________________________

liquid tissue marker (BioXmark®, Nanovi®, Copenhagen, DK ) to define the local cavity for the purpose for defining a boost volume or a target volume suitable for APBI. Material and Methods Preclinical investigations how to apply BioXMark® liquid marker best for visualization by computer tomography were performed. Subsequently, thirteen patients underwent lumpectomy for limited stage breast cancer disease and the tumor cavity was marked with the liquid marker as well as a surgical clip. All patients were older than 50 yrs, and all patients presented with hormone- receptor positive disease less than 3 cm, pN0 and all were potentially suitable for APBI. The tumor cavity was marked immediately after resection with BioXmark® and surgical clips. The liquid marker was placed before any oncoplasty-manipulation was performed in three patients analysed. A planning CT was performed 4-5 weeks after surgery. The boost volume was defined, according to the metal clips and the area marked by BioXmark. Results In preclincal studies a phantom was used to see that the liquid marker sprayed over several square centimeters achieved best Imaging qualities on comptuer tomgraphy. Thus, applying a film of liqud marker over the surface of interest was chosen for further clincal investigations. Seven patients were analysed by the time of submission. The tumor cavity was clearly marked for the purpose of tumor cavity segmentation in six out of seven cases. In one patient, the marker was not reliabely discrimiated from the glandular tissue. The mean volume or the tumor bed was 22,69 ml (range 8,1 - 40,96). In respect to the metal clips placed on the thoracic wall after lumpectomy, considerable displacement of the boost target volume after oncoplasty was visualized. Conclusion Visualization of the tumor cavity can improve on the accuracy of the target volume definition for APBI and may allow optimizing PTV margins. Further investigation is justified to reveal clinical utility of liquid-marker- based target volume definition after lumpectomy. EP-1180 Whole breast radiotherapy in Lateral Decubitus position : efficacy and toxicity E. Bronsart 1 , S. Dureau 2 , H. Xu 1 , F. Berger 2 , F. Campana 1 , E. Costa 1 , A. Chilles 1 , A. Fourquet 1 , Y. Kirova 1 1 Institut Curie, Radiation therapy, Paris, France 2 Institut Curie, Biometrics, Paris, France Purpose or Objective To evaluate whole breast 3D conformal radiotherapy (RT) delivered in lateral decubitus position (Isocentric Lateral Dubitus ILD) and report the acute and the late cardiac and pulmonary toxicity of a cohort of patients treated with ILD. Material and Methods From 2006 to 2010, 832 patients with early-stated breast cancer treated by conservative surgery underwent 3D- conformal whole breast RT in the lateral decubitus position at Institut Curie. All types of cup size was included. The acute toxicity of treatement was evaluated weekly using NCI CTC v3.0 scale, and the late toxicity was evaluated once a year and started one year after the end of RT. A dosimetric study was performed to analyse the mean cardiac dose and the mean homolateral and controlateral lung doses. Results median of follow up is 6.4 years, median age is 61,5 years (min29-max90), and median body mass index is 26.3. 51% have left breast cancer and 49% have right breast cancer. Different type of fraction/dose were performed : 46.5% 66Gy in 33 fractions, 17.9% 50Gy in 25 fractions, 26.1% 40 or 41.6Gy in 15 or 13 fractions and 30Gy in 5 fractions. Acute epidermitis was present in 93% with a median of apparition of 4 weeks, and only 2,8% grade 3. In multivariate analysis, the cup size has signicative

influence (p=0,0004) and the fractionation has a significative influence (p=0,0001). After one year 94.1% had no epidermitis. No cardiac or pulmonary toxicity was reported. For normofractionation (2Gy fractions, 50 Gy on the whole breast and 16Gy boost on the tumor bed) : Mean dose to homolatéral lung (HL) is 1,4 Gy (min 0,63 Gy-max 3 Gy), mean dose to controlateral lung (CL) is 0,07Gy (min0,37Gy-max1Gy) mean cardiac dose is 1,14 Gy (min0,54 Gy – max4 Gy). In hypofractionation : for 41,6Gy in 13 fractions schedule : mean dose to HL is 0,87Gy (min0,38 Gy-max5 Gy), mean dose to CL is 0,03 Gy (min0,3 Gy-max3 Gy) mean cardiac dose is 0,77 Gy (min0,38 Gy- max9 Gy). For 40 Gy en 15 fractions schedule : mean dose to HL is 0,96 Gy (min0,38 Gy-max4 Gy), mean dose to CL is 0,04 Gy (min0,02 Gy-max2,28 Gy) mean cardiac dose is 0,74Gy (min0,3 Gy-max1 Gy). In the 28,5Gy en 5 fractions schedule : Mean dose to HL is 0,53Gy (min0,26Gy- max3Gy), mean dose to CL is 0Gy (min0 Gy-max0,4 Gy) mean cardiac dose is 0,37Gy (min0,6 Gy-max5 Gy). Median overall survival is not reached, there is no influence of fractionation on overall survival. Relapse-free survival is not reached, with only 36 relapses without influence of fractionation. Conclusion whole breast radiotherapy in the lateral decubitus position provides excellent results with very low mean cardiac dose and mean pulmonary dose. There is no cardiac or pulmonary toxicity in this study. And it’s also very well tolerated with very good acute toxicity profile. EP-1181 dose to non-routinely delineated risk organs in post left conservative surgery conformal breast RT M. Abdelwahed 1 , M.A.H. Mohamed Abdelrahman Hassan 2 1 As-Salam International Hospital, oncology, Cairo, Egypt 2 Kasr Alaini Center of Clinical Oncology & Nuclear Medicine NEMROCK, clinicla oncology, cairo, Egypt Purpose or Objective This is a dosimetric study aiming at evaluation of radiation doses to risk organs particularly (brachial plexus, coronary artery & thyroid gland) in previously treated breast cancer cases at Kasr Alaini Center of Clinical Oncology & Nuclear Medicine after left Breast Conservative Surgery (BCS) Our aim was to identify the patients' subgroups in need for routine delineation of these risk organs to avoid toxic doses to them. Material and Methods Twenty five female patients with left BCS treated with external beam radiotherapy to the left breast and supraclavicular region. Delineation of the coronaries was done according to the University of Michigan Medical Center; while the brachial plexus was delineated according to the RTOG guidelines. Patient measures like body mass index (BMI), mid beam cut separation, Central lung distance, Maximum heart distance (MHD) and doses to risk organs were documented (Heart V 30 & heart D mean , brachial plexus D max , thyroid gland D mean ,…) Results Age of the patients ranged from 35years to 70 years (median=54years). BMI ranged from 22.1 to 47.6 (mean=34.2±6.7). MHD mean value was 2.9±1.1cm while the heart V 30 mean value was 3.44±3.59% with heart D mean range from 1.2 up to 9.00Gy (mean=3.92±2.02Gy). The anterior descending coronary artery (ADCA) D max was 41.9±6.60Gy while the ADCA D mean was 23.4±10.9Gy. ADCA D mean increased from 18.5±10.9Gy with MHD ≤3cm to 27.9±9.1Gy with MHD >3cm (ρ-value 0.030). ADCA D mean was also related to V 30 of the heart as the ADCA Dmean was 16.9±10.5Gy with V 30 <2% while ADCA D mean was 29.5±7.3Gy with V 30 ≥2% (ρ-value=0.005). BMI showed borderline significance on ADCA D max when the BMI was <30, the ADCA D max was 37.3±10.0Gy while it was 43.7±43.7Gy when BMI ≥30 with a ρ-value 0.074. None of the outcome parameters had clinical significance related to the thyroid gland or brachial plexus, The