Abstract Book

S712

ESTRO 37

Material and Methods An electronic questionnaire was completed by experienced radiation oncologists from twelve RT centers, covering a reference population of about 7,500,000 inhabitants. The items surveyed the professional experience, therapeutic approach, technique, dose and stereotactic body RT (SBRT) availability. Controversy in clinical practice is summarized in the figure 1.

Purpose or Objective To analyse the local relapse by molecular subtypes in breast cancer (BC) patients (pts) treated conservatively. Material and Methods Retrospective comparative analysis of 940 pts with breast cancer stage I-II, treated with conservative surgery plus radiotherapy from January 1995 to December 2012 in our hospital. Molecular subtypes were: luminal A (63.5%), Luminal-B (21%), HER2 (3.6%) and triple negative (TN) (11.9%). Survival rates were estimated with Kaplan-Meier and compared with Log Rank test. Prognostic factors such as age, tumour stage, grade, histology, radiotherapy total dose, margin status, hormonotherapy and chemotherapy have been related to local disease free survival (LDFS) and overall survival (OS) using Cox regression Results At a median follow-up of 117 months for Luminal-A, 69.7 for luminal B, 99.1 for TN and 90.4 months for HER2. 21 pts (2.2%) had local recurrence (Luminal-A: 1.8%, Luminal-B 1.5%, HER2 2.9%, TN 5.4%) and 64 pts (6.8%) had distant recurrence (Luminal-A: 7.4%, Luminal-B 4.1%, HER2 14.7%, TN 6.3%). 8-years LDFS and OS were Luminal-A: 99% and 91.7%, Luminal-B 97% and 87.5%, HER2 96.9% and 67.8% (p=0.001), TN 96.9% and 86.9% (p=0.004) respectively. In the multivariate analysis tumour stage (p=0.007), grade (p=0,003), age (p=0.000) and molecular subtype HER2 (p=0.007) were significant prognostics factors of OS and molecular subtype TN of LDFS (p=0.008). Conclusion According to our results, local relapse as the first site of failure in early breast cancer after conserving therapy was significantly more frequent in triple negative in comparison with other molecular subtype. EP-1299 Postmastectomy radiation therapy after subcutaneous direct-to-implant breast reconstruction I. Meattini 1 , M. Bernini 2 , D. Casella 3 , V. Maragna 1 , S. Sordi 2 , I. Desideri 1 , I. Gaggelli 2 , L. Dominici 1 , A. Fausto 4 , C. Delli Paoli 1 , E. Olmetto 1 , G. Francolini 1 , M. Loi 1 , V. Scotti 1 , D. Greto 1 , P. Bonomo 1 , G. Simontacchi 1 , J. Nori 5 , S. Bianchi 6 , L. Livi 1 1 Azienda Ospedaliero Universitaria Careggi - University of Florence, Radiation Oncology Unit - Oncology Department, Florence, Italy 2 Azienda Ospedaliero Universitaria Careggi - University of Florence, Breast Surgery Unit, Florence, Italy 3 Livorno Hospital, Breast Surgery- Breast Unit, Livorno, Italy 4 Le Scotte University Hospital, Diagnostic Imaging, Siena, Italy 5 Azienda Ospedaliero Universitaria Careggi - University of Florence, Diagnostic Senology Unit, Florence, Italy 6 Azienda Ospedaliero Universitaria Careggi - University of Florence, Pathology Division, Florence, Italy Purpose or Objective Subcutaneous direct-to-implant breast reconstruction is a brand-new fascinating breast reconstructive surgical approach. An expander/implant (E/I)-based breast reconstruction accounts for around 70% of all reconstructions. However, acute and long-term complications rates still remain a concern, especially if postmastectomy radiation therapy (PMRT) is delivered. Moreover, PMRT indication is increasing over time, since improved disease free-survival has been demonstrated also in the case of a limited axillary involvement. The aim of our study is to report the safety of PMRT after subcutaneous breast reconstruction using E/I and PMRT. Material and Methods We performed a retrospective analysis on 345 consecutive non metastatic breast cancer patients (T1-3, N0-3) treated by multimodal approach at the University of Florence between January 2012 and May 2016. All patients received mastectomy with immediate

Figure 1. Management flow for bone metastatic breast cancer patients based on the survey. The dashed line symbolizes the subjects of controversy. ST: systemic therapy. OM: oligometastases. CR: complete response. PR: partial response. RT: radiotherapy. EBRT: external beam radiotherapy. SBRT: stereotactic body radiotherapy. Results Nine of the twelve centers advise and administer RT for oligometastases, while two RT centers advise but refer for SBRT elsewhere. Regarding asymptomatic bone oligometastases, 8/12 advise RT only for 'risky lesions”, such as pending fractures or spinal cord compression. Eight/twelve RT centers start first with systemic treatment, particularly for asymptomatic bone metastases. The approach to bone metastases showing a complete response after systemic treatment was closer (7/12 centers postponing RT until the patient presents with signs or symptoms of progression). Only in 4/12 centers SBRT is available with spinal techniques. Conclusion There is a lack of consistency in the approach to treatment of breast cancer patients with bone-only oligometastases. This can be explained by the absence of evidence-based guidelines and an incomplete availability of SBRT. EP-1298 Local Relapse By Biological Subtypes In Breast Cancer Patients M.C. Cruz muñoz 1 , J.L. Muñoz Garcia 2 , M.A. Gonzalez Ruiz 2 , P. Simon Silva 2 , A. Corbacho Campos 2 , F. Ropero Carmona 2 , J. Quirós Rivero 2 , Y. Ríos Cavadoy 2 , J.J. Cabrera Rodriguez 2 , B. Ortiz Sierra 2 1 Hospital Infanta Cristina, Oncology Radiotherapy, utrera, Spain 2 Hospital Infanta Cristina, Oncology Radiotherapy, Badajoz, Spain