Abstract Book

S710

ESTRO 37

Hernanz De Lucas 1 , A. Montero Luis 1 , S. Sancho García 1 1 Hospital Ramon y Cajal, Radiation Oncology, Madrid, Spain 2 Hospital Ramon y Cajal, Statistical Department, Madrid, Spain 3 Hospital Ramon y Cajal, Pathology Department, Madrid, Spain Purpose or Objective Prediction of patients at highest risk for ipsilateral breast tumor recurrence (IBTR) after local excision of ductal carcinoma in situ (DCIS) remains a clinical concern. The aim of our study was to evaluate the nomogram from Memorial Sloan Kettering Cancer Center (MSKCC) to predict the risk of IBTR in a Spanish population with DCIS in our institution. Material and Methods We retrospectively identified 307 patients diagnosed of DCIS who had undergone surgery from 2000 through 2011 at the Ramón y Cajal University Hospital (Madrid). Clinic and pathologic factors and performance of the MSKCC nomogram for prediction of IBTR were assessed. Results Median follow-up time was 112 months. Among the 306 patients, 50 (16.33%) developed recurrence. IBTR was present in 38 patients (12.41%), 20 of those had DCIS and 18 had invasive recurrence. We evaluated our data set with the MSKCC model. Because of missing data, 1 of the 306 patients was excluded. The 5- and 10-year probabilities of recurrence for the 305 patients who had complete data were calculated with the MSKCC nomogram. Only patients with ipsilateral recurrence were included in our validation. Calibration for 5- and 10- year probability of breast recurrence for the nomogram showed good model calibration with intermediate correlation of nomogram-predicted probability of breast recurrence and observed probability of breast recurrence as estimated by the Kaplan-Meier method. The best correlation was in terciles. We have stratified patients in three groups: low risk as < 5% of risk of recurrence, intermediate risk between 6-10% and high risk with > 11%. Conclusion The MSKCC nomogram shows validity in our population and allows users to integrate the information from 10 different variables to provide precise risk stratification. We have validated the MSKCC nomogram in our Spanish population and we are considering new lines of study. EP-1296 Unintended dose to the lower axilla in whole breast radiotherapy: standard tangential fields vs VMAT I. Ahrouch 1 , O. Koshariuk 2 , D. Van Gestel Dirk 3 , A. De Caluwé 3 1 UCL Cliniques Univ. St.Luc, Radiation Oncology, Brussels, Belgium 2 ULB Insitut Jules Bordet, Radiation Oncology, Brussels, Belgium 3 ULB Institut Jules Bordet, Radiation Oncology, Brussels, Belgium Purpose or Objective Omission of axillary clearance in patients with one or two positive sentinel lymph nodes after breast conservative surgery is based on clinical trials (such as the ACOSOG Z0011 trial) in which all patients received adjuvant whole breast radiotherapy (WBRT) with tangential fields. In these trials, treatment in prone position or with partial breast irradiation was not allowed. Hence, unintentional coverage of axillary levels I and II by tangential fields has been suggested to contribute to the low rate of axillary recurrence. Volumetric modulated arc therapy (VMAT) is increasingly used in the adjuvant treatment of breast cancer, in

LVI. Approximately 61.9% (n = 39) of the patients’ samples stained positive for p53. Additional chemotherapy and radiotherapy (RT) were performed in 53 (84.1%) and 47 (74.6%) patients, respectively. Results The median follow-up period was 39.5 (range: 5.9–123.0) months. The pathological T stage (p = 0.008), N stage (p = 0.014), and p53 positivity (p = 0.044) were associated with LVI. Overall, the 3-year disease-free survival (DFS) rate and overall survival (OS) rate were 85.4% and 90.2%, respectively. Ten patients (15.9%) experienced relapse. LVI (n = 12) was associated with relapses (p = 0.016). p53 positivity was correlated with poor DFS (p = 0.048). Furthermore, LVI was related to poor DFS (p = 0.011) and OS (p = 0.001) and considered as an independent prognostic factor for DFS (p = 0.039). The 3-year DFS of patients with LVI (n = 12) was only 58.3%. Adjuvant RT minimized the negative prognostic effect of LVI on DFS (p = 0.068 [with RT] vs. p = 0.011 [without RT]). Conclusion LVI was related to the detrimental effects of disease progression and survival of TNBC patients. Thus, a more effective treatment strategy is needed for TNBC patients with LVI. EP-1294 Accelerated partial breast irradiation (APBI) with SBRT and Gating in early breast cancer patients R. Ciervide 1 , A. Montero 1 , M. García-Aranda 1 , M. López 1 , J. Valero 1 , E. Sánchez 1 , X. Chen 1 , O. Hernando 1 , R. Alonso 1 , B. Alvarez 1 , A. Acosta 1 , C. Rubio 1 1 Hospital Universitario Madrid Sanchinarro - Grupo Hospital de Madrid, Radiation Oncology depatment, Madrid, Spain Purpose or Objective Asses the feasibility of applying SBRT with Gating in patients with breast cancer of very good prognosis with 5 fractions of 6 Gy in alternate days. Reduce the PTV margin by quantifying the breast movement during the respiratory cycle (RC) and to irradiate in a selected phase of that cycle. Identify and quantify toxicity and cosmesis Material and Methods Patients with ≥60years, pT1 breast tumor after breast conserving surgery, surgical margins ≥2mm, pathological confirmation of infiltrating ductal carcinoma, grade 1-2, pN0, ECOG 0-1 and luminal subtype are enrolled. A gold fiducial marker is placed close to the surgical bed. CT simulation is done in supine position with an immobilization device and infrared spheres on the skin, as external fiducials. The radiation treatment is planned with iPlan Net® and DVH are assessed according to ASTRO recommendations for PBI constraints. During treatment delivery, PTV intrafraction motion is controlled with NovalisExactrac Gating System and PTV is irradiated in a selected gated area of the RC. Clinical and toxicity outcomes are assessed periodically. Results A total of 23 patients with a median of 74 years old (range 60-86) were included. The median tumor size was 1,2cm (range 0,5-2cm). 13 cases were right breast and 10 left side. The mean PTV volume was 95,3cc. The mean ipsilateral lung V9 was 2Gy.With a median follow up of 25,4 months, there was just 1 regional relapse after 25,1 months. She was treated by mastectomy and is free of disease. There was no toxicity greated than grade 1 and cosmesis was excellent from the patient and physician point of view. Conclusion APBI with SBRT and Gating is not only feasible but also very well tolerated and accepted for patients. EP-1295 Validation of the MSKCC-nomogram in the prediction of recurrence risk after treatment in DCIS. C. De la Pinta Alonso 1 , E. Fernández-Lizarbe 1 , A. Muriel 2 , B. Pérez 3 , M. Martín Sánchez 1 , T. Muñóz Migueláñez 1 , R.