ESTRO 36 Abstract Book

S119 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective Post-operative radiation therapy (PORT) is often used for breast cancer patients who received neoadjuvant chemotherapy (CT) followed by surgery. Nevertheless, the optimal time to initiation of PORT is unclear. Material and Methods Between 2008 to 2014, data from non metastatic breast cancer patients who underwent PORT after neoadjuvant CT and surgery were assessed retrospectively. Patients were categorized into three groups according to the time between surgery and PORT: <8 weeks, 8-16 weeks and >16 weeks. The primary endpoint was disease free survival (DFS). Multivariate Cox regression adjusted for molecular profile, histological grade (HG), age, clinical stage and complete pathologic response (pCR) was used to estimate survivals outcomes. Binary logistic regression model was used to calculate the adjusted odds ratios for recurrence. Results Among the 581 patients included, the vast majority had clinical stage III (75%) and received antracycline-taxane based neoadjuvant CT (95%). Forty-three patients received PORT within 8 weeks, 354 in 8-16 weeks and 184 after 16 weeks from surgery. With a median follow-up of 32 months, beginning radiation therapy up to 8 weeks after surgery was associated with better DFS (HR 0.36; 95%CI 0.146-0.914; p=0.03) and a trend in better OS (HR 0.223; 95%CI 0.07-1.14; p=0.08). The factors associated with less recurrence rate were: PORT at 8 weeks (OR=0.33; 95% CI 0.12-0.90; p=0.03), stage I-II (OR=0.41; 95%CI 0.25-0.69; p=0.001) and pCR (OR=0.15; 95%CI 0.07- 0.32; p<0.001). Conclusion PORT started up to 8 weeks after surgery was associated with better DFS and a trend in better OS in a predominantly stage III population of breast cancer patients submitted to neoadjuvant CT. Our findings suggest that early initiation of radiation therapy should be granted for these patients. PV-0237 Management and outcome of local failure after intraoperative partial breast irradiation M.C. Leonardi 1 , L. Tomio 2 , G.B. Ivaldi 3 , G. Catalano 4 , M. Alessandro 5 , C. Fillini 6 , A. Ciabattoni 7 , M. Guenzi 8 , C.M. Francia 9 , C. Fodor 10 , F. Rossetto 10 , B.A. Jereczek –Fossa 9 , R. Orecchia 11 , AIRO IORT Working Group 12 1 Istituto Europeo di Oncologia - IEO, Division of Radiotherapy, MIlan, Italy 2 Santa Chiara Hospital, Radiotherapy Unit, Trento, Italy 3 Fondazione Salvatore Maugeri, Oncology unit, Pavia, Italy 4 Multimedica Holding Clinical Institute, Unit of Radiotherapy, Castellanza, Italy 5 Ospedale di Città di Castello, Radioterapia Oncologica, Città di Castello, Italy 6 Azienda Ospedaliera Santa Croce e Carle, Department of Radiation Oncology, Cuneo, Italy 7 San Filippo Neri Hospital, Department of Radiotherapy, Rome, Italy 8 IRCC Azienda Ospedaliero-Universitaria San Martino IST, UOC Oncologia Radioterapica, Genoa, Italy 9 European Institute of Oncology - University of Milan, Department of Radiation Oncology - Department of Oncology and Hemato-oncology, Milan, Italy 10 European Institute of Oncology, Department of Radiation Oncology, Milan, Italy 11 European Institute of Oncology - University of Milan, Department of Medical Imaging and Radiation Sciences - Department of Oncology and Hemato-oncology, Milan, Italy 12 Associazione Italiana Radioterapia Oncologica, intraoperative radiotherapy working group, -, Italy’ Purpose or Objective To assess the outcome and the patterns of failure in patients (pts) who develop an ipsilateral in breast

recurrence (IBTR) after breast conservative surgery (BCS) partial breast irradiation (PBI) with intraoperative radiotherapy with electrons (IORT). Material and Methods The Italian IORT Working Group promoted collection of information regarding clinical management and outcome of pts who experienced a failure of breast conservative treatment after being given IORT as sole radiotherapy (full dose at 21 Gy). Data from 8 Italian radiation centers were recorded in a central dedicated database for a total of 228 pts. Pts gave informed consent for the use of anonymized data for research and training purposes. Clinical outcomes included IBTR, nodal failure, distant metastases, disease- free survival and overall survival. Treatment options were recorded. Results Median time from BCS with IORT full dose (21 Gy) to IBTR was of 3.9 years (range 0.4-15 years). 128/228 pts (56.1%) experienced a true/marginal miss IBTR, 51/228 (22.3%) presented local relapse in a breast site far from the index quadrant, 8/228 (3.5%) relapsed with lymphangitis features. In about 15% of cases, local relapse was combined with nodal regional or distant metastases. Axillary failure alone was observed in 4 pts (1.7%), while bone metastases without locoregional recurrence in only 1 case (0.4%). Surgical salvage therapy was carried out with different modalities. Mastectomy was performed in 129/228 patients (56.5%), 7.4% of them received also postmastectomy radiotherapy. Second conservative surgery with or without axillary investigation was given to 88 patients (38.5%). Interestingly, patients re-operated on conservatively received additional radiotherapy: 44 (19.2%) were treated with whole breast irradiation (WBRT), using conventional or hypofractionated schemes, while 22 (9.5%) were treated with PBI, using either intraoperative radiotherapy with electrons or conformal external beam radiotherapy. Only 8 pts didn’t undergo reoperation due to disease progression. Median follow-up after salvage surgery was 3.5 years (0-12 years). In this time frame, 3.3% of pts developed a second isolated local relapse, while in other 3.3% of cases the second local relapsed combined with another event (nodal, distant, contralateral tumor reappearance). Distant metastases as first site of failure after salvage treatment occurred in 12.2% of pts. Status at last follow-up was: 70% alive without disease, 16% alive with disease, 12% died of disease. Conclusion Treatment failure mostly consisted of local I n breast reappearance at or near the irradiated site. While most of pts received salvage mastectomy, second BCS with additional radiotherapy, either WBRT or PBI, is feasible. Overall survival was lower than that reported by the randomized ELIOT trial and therefore a multivariate analysis is being performed to identify predictor and prognostic factors. PV-0238 Use of Stereotactic Ablative Radiotherapy in Non-Small Cell Lung Cancer Measuring 5 cm or More H. Tekatli 1 , S. Van 't Hof 1 , E.J. Nossent 2 , M. Dahele 1 , W.F.A.R. Verbakel 1 , B.J. Slotman 1 , S. Senan 1 1 VU University Medical Center, Radiation Oncology, Amsterdam, The Netherlands 2 VU University Medical Center, Pulmonology, Amsterdam, The Netherlands Purpose or Objective Stereotactic ablative radiotherapy (SABR) is currently not the guideline recommended treatment for lung tumors measuring 5 cm or more. However, improvements in treatment planning and delivery have enabled better sparing of normal organs, leading to an increased use of SABR for these tumors.