ESTRO 36 Abstract Book

S2 ESTRO 36 2017 _______________________________________________________________________________________________

delineated. In Phase 1 nine radiation oncologists defined the target volumes of five patients without any instructions, while in Phase 2 four observers draw the contours of four patients applying simple contouring rules. The delineations were compared between the two phases, the impact of guidelines was assessed and cavity visualization score was related to consistency of delineations. Following the study on interobserver variations of target volume delineation and a number of discussions in consensus meetings guidelines were worked out by experts on the field. Recommendations : (1) Consistent windowing has to be used for proper cavity visualization. (2) The cavity visualization score has to be at least 3 in order to minimize the interobserver variations of target definition. (3) At delineation of surgical cavity only the homogeneous part of the postoperative seroma has to be included in the contours and protrusions or sharp irregularities have to be excluded. When surgical clips are present, they have to be surrounded by the contour with close contact. (4) CTV is created from the outlined surgical cavity with a non- isotropic geometrical extension. In each direction the safety margin is calculated by taking into account the size of free resection margin. The total size of safety margin is always 20 mm which is the sum of the surgical and added safety margins. CTV is limited to chest wall/pectoral muscles and 5 mm below the skin surface. Conclusion : It has been demonstrated that simple rules on defining the lumpectomy cavity significantly increased the consistency of contouring. Reliable consistency of target volume definition can be expected only for good cavity visibility. Following the GEC-ESTRO guidelines it is expected that the target volume definition in breast brachytherapy after open cavity surgery will be accomplished with more consistent way among radiation oncologists with low interobserver variations. SP-0010 The gains to be made by combined modality treatment in NSCLC: setting the scene of new possibilities M. Stuschke 1 , C. Poettgen 1 1 Universitätsklinikum Essen, Radiotherapy, Essen, Germany Concurrent radiochemotherapy or combined modality treatments including surgery are standard options for stage IIIA NSCLC and stage IIIB patients treated with curative intent. Cumulative incidences of loco-regional recurrences approach 30% at 5 years following standard concurrent 60 Gy radiochemotherapy with conventional fractionation, while tri-modality schedules showed loco- regional recurrences of about 15%. Dose escalation using conventional fractionation and concurrent platin-based chemotherapy within the RTOG 0617 trial has failed to show a benefit in survival or local control. Passive scattering Proton therapy did not show a reduction in the rate of radiation pneumonitis in comparison to intensity modulated photon radiotherapy at the same total dose according to the NCT 00915005 trial. So where are the promising ways to improve survival of patients with locally advanced lung cancer by technological advances in radiotherapy? More sensitive methods are needed to detect tumor spread and beyond FDG-PET/CT. Systematic endobronchial ultrasound-guided transbronchial needle aspiration can improve sensitivity to detect lymph node metastases. Prognostic factors for tumor control and toxicity after concurrent radiochemotherapy are being established to individualize dose escalation. PET- response, tumor volume, and dose volume histogram Joint Symposium: ESTRO-ASTRO: Cutting edge combined modality therapies (Focus on NSCLC)

Teaching Lecture: Target delineation and target definition for Partial Breast Irradiation after closed cavity surgery and oncoplastic surgery SP-0008 Target delineation and target definition for Partial Breast Irradiation after closed cavity surgery and oncoplastic surgery V. Strnad 1 1 University Clinic Erlangen, Dept. Radiation Oncology, Erlangen, Germany Objective: To define in CT images tissue structures inside the breast after a breast conserving surgery, which make possible reproducible delineate Clinical Target Volume (CTV) and Planning Target Volume (PTV). The results of deliberations of Breast Working Group of GEC-ESTRO and corresponding recommendations for target definition for APBI will be presented. Recommendations: The Working Group Breast of GEC- ESTRO recommend to have for the correct delineation of CTV (PTV) appropriate knowledge’s and to perform steps As follow: 1. To hold DETAILED KNOWLEDGE’ S about anatomy of the breast of patient and of the tumor, about primary surgical procedure particularly type of surgery, use - number and location of surgical clips, position of the skin scar ), of pathological report (particularly size of resection margins in at least 6 directions, of preoperative mammography, MRI and ultrasound. 2. Identification of the TUMOR LOCALIZATIO N before breast conserving surgery inside the breast and translate this information in current CT imaging data set. 3. Calculation of the size of SAFETY MARGINS needed to cover CTV in all 6 directions. The appropriate size of safety margins (surgical resection margins and adapted safety margins) should be at least 2 cm. 4. DEFINITION OF TARGET 5. DELINEATION OF THE TARGET according defined rules. We recommend following seven steps for target delineation after closed cavity surgery: a. Perform a CT. b. Delineation of clips. c. Delineation of surgical bed – whole surgical scar (WS) inside breast. d. Delineation of ImTV (Imaging correlated Target Volume). For target definition after oncoplastic surgery dissident from recommendation for target definition after “closed cavity surgery” the Clinical target volume (CTV) is defined as the sum of the relevant clipped area (RCA). Conclusion: Presented guidelines makes possible a reproducible and robust definition of CTV (PTV) for Accelerated Partial Breast Irradiation (APBI) or boost irradiation after breast conserving closed cavity or oncoplastic surgery. SP-0009 Target delineation and target definition for PBI after open cavity surgery T. Major 1 , C. Polgár 1 1 National Institute of Oncology, Radiotherapy Centre, Budapest, Hungary Objective : To present guidelines for target definition and delineations after open cavity breast conserving surgery in accelerated partial breast irradiations or boost treatments using multicatheter interstitial brachytherapy based on the consensus of the GEC-ESTRO Breast Cancer Working Group. Method: As a first step a contouring study with two phases was conducted by the Working Group. Contours of cavity and PTV on pre- and postimplant CT images were e. Delineation of ETB (Estimated Tumour Bed). f. Delineation of CTV (Clinical Target Volume). g.Delineation of PTV (Planning Target Volume).