ESTRO 37 Abstract book

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ESTRO 37

Material and Methods One hundred sixteen patients were treated with DIBH technique, from January 2016 to September 2017. We retrospectively analyzed 50 patients treated on whole breast plus surgical bed. The prescribed dose was 50 Gy to PTV II and 10-16 Gy to PTV I, 2 Gy/fraction. For each patient the treatment technique, 3DCRT or VMAT, has been chosen according to ICRU recommendations. Finally two homogeneous groups were compared: 24 patients treated with the 3DCRT modality and 16 with the VMAT one. The median PTVII, PTVI and OAR volumes were comparable in both groups. These dosimetric parameters have been analyzed to compare the two different techniques: Dmean heart, Dmax heart, V30 heart, V20 heart, V10 heart, Dmax LAD, Dmean ipsilat lung, D2% ipsilat lung, V30 ipsilat lung, V20 ipsilat lung, V5 ipsilat lung, Dmean contralat lung, D2% contralat lung, V5 contralat lung, Dmean contralat breast, D2% contralat breast, V5 contralat breast. A Mann-Whitney statistical test was used and statistical p value < 0.01 was considered significant. Results 3DCRT achieved a statistically significant dose reduction for the following parameters: D mean heart, V 20 heart, V 10 heart, D max LAD, D mean ipsilat lung, V 20 ipsilat lung, V 5 ipsilat lung, D mean contralat lung, D 2% contralat lung, V 5 contralat lung, D mean contralat breast, D 2% contralat breast, V 5 contralat breast. Conversely VMAT get a statistically significant advantage for D 2% ipsilat lung. 3DCRT and VMAT plans were comparable for other parameters: Dmax heart, V30 heart and V30 ipsilat lung. Table1 Conclusion In our experience 3DCRT technique allows good results in terms of OAR sparing if associated with DIBH modality. A comparison with VMAT is mandatory for improving, if the case, the PTV dose distribution homogeneity. EP-1331 Role of postoperative radiotherapy in DCIS: an observational study of 1,048 cases S. Corradini 1 , M. Pazos 1 , S. Schönecker 1 , D. Reitz 1 , M. Niyazi 1 , U. Ganswindt 1 , M. Braun 2 , N. Harbeck 3 , J. Engel 4 , C. Belka 1 1 LMU Munich, Department of Radiation Oncology, Munich, Germany 2 Red Cross Hospital, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany 3 LMU Munich, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany 4 LMU Munich, Munich Cancer Registry MCR of the Munich Tumour Centre TZM at the Institute of Medical Information Processing- Biometry and Epidemiology IBE, Munich, Germany Purpose or Objective The objective of the present study was to evaluate the effectiveness of postoperative radiotherapy after breast conserving surgery (BCS) in DCIS in a large patient population treated in clinical practice. Material and Methods Data were provided by the population-based Munich Cancer Registry. Between 1998 and 2014, 1048 female patients with diagnosis of DCIS and treated at two Breast Care Centres were included in this observational study. The effectiveness of postoperative radiotherapy and variables predicting the use of radiotherapy were retrospectively analysed. Median follow-up was 85.5 After adjusting for age, tumour characteristics and therapies, Cox regression analysis for local recurrence- free survival identified RT as an independent predictor for improved local control (HR: 0.612; 95%CI: 0.399- 0.939, p=0.025). Ten-year cumulative incidence of in- breast recurrences was 14.6% following BCS, compared to months. Results

9.1% in patients receiving postoperative radiotherapy (p=0.017). As an estimate for disease-specific survival, 10-year relative survival was 105.4% for patients receiving postoperative radiotherapy and 101.6% without radiotherapy. On multivariate analysis, postoperative radiotherapy was not associated with improved overall survival (HR 0.526; 95%CI: 0.263-1.052, p=0.069). Over time, a significant increase of RT was registered: while 1998 only 42.9% of patients received postoperative radiotherapy, the proportion rose to 91.2% in 2014. Women aged <50 years (OR: 1.616, 95%CI: 1.054-2.477, p=0.004) or with negative hormone receptor status (OR: 2.124, 95%CI: 1.305-3.457, p=0.002) were more likely to receive postoperative radiotherapy after BCS. Conclusion In conclusion, this study provides insights regarding the adoption and treatment pattern of postoperative RT following BCS for DCIS in a large cohort reflecting "real- life" clinical practice in this setting. Postoperative RT was found to be associated with a reduced risk of ipsilateral recurrence and no survival benefit compared to observation alone. EP-1332 Efficacy of an accelerated hypofractionted schedule for whole breast and regional node irradiation A. Montero Luis 1 , M. Hernandez 2 , R. Ciervide 1 , M. Garcia- Aranda 1 , B. Alvarez 1 , J. Valero 1 , A. Acosta 1 , R. Alonso 1 , M. Lopez 1 , E. Sanchez 1 , O. Hernando 1 , C. Rubio 1 1 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Oncology, Madrid, Spain 2 University Hospital Rey Juan Carlos, Radiation Oncology, Madrid, Spain Purpose or Objective Regional nodal irradiation (RNI) in node-positive women with breast cancer is indicated to improve loco-regional control and survival. Hypofractionated whole breast radiotherapy appears as a standard treatment, although there is still controversy about its use for regional nodal irradiation. We present our results in terms of acute toxicity and local control of RNI with a hypofractionated accelerated radiotherapy schedule. Material and Methods From January-2015 to December-2016, 140 patients with a median age of 50 years (range 31-84) were treated according to our institution hypofractionated radiotherapy schedule. Clinical staging (AJCC): 5p (3.6%) stage 0; 31p (22.1%) stage IA; 39p (27.9%) stage IIA; 43p (30.7%) stage IIB; 15p (10.7%) stage IIIA; 5p (3.6%) stage IIIB and 2p (1.4%) stage IV. All patients underwent breast surgery, both conservative tumorectomy (63p, 45%) or mastectomy (77p, 55%). Ninety-eight patients (70%) underwent complete axillary lymph node dissection (ALND) whereas 42p (30%) underwent selective sentinel lymph node biopsy exclusive. Histology: 115p (82.17%) infiltrating ductal carcinoma, 20p (14.3%) infiltrating lobular carcinoma and 5p (3.6%) ductal carcinoma in-situ. Molecular subtypes: Luminal A 48p (34.3%), Luminal B 54p (38.6%), Her2-enriched 16p (11.4%) and triple-negative 22p (15.7%). Radiotherapy comprises the whole breast or chest wall and the regional nodes levels I-IV up to a total dose of 40.5Gy@2.7Gy/day. In 12p (8.6%) irradiation of internal mammary chain was considered according to pN2-3 axillary affectation or tumors of central-inner quadrants. Simultaneous integrated boost (SIB) was administered to all patients after BCS and to 3 patients with close/focally affected margins after mastectomy, total dose of 48Gy@3.2Gy/day in 62p and 51Gy@3.4 Gy/day in 4p. Systemic therapy: 116p (82.9%) received chemotherapy either neoadjuvant (51p, 36.4%) or adjuvant (65p, 46.4%); 108p (77.1%) hormone therapy (tamoxifen 52p, aromatase inhibitors 56p)