ESTRO 36 Abstract Book

S636 ESTRO 36 2017 _______________________________________________________________________________________________

assisted breast cup and imaged on a CT simulator with 1 mm slice thickness. Once the cup is placed, the negative pressure is maintained until the treatment is delivered. An inversely optimized treatment plan is generated while the patient is transported and positioned in the treatment room. Typical time between the imaging session and completion of treatment is about 60 minutes. Results 5 of the first 6 enrolled patients completed the treatment. One patient’s lumpectomy cavity extended outside the immobilized portion of the breast and therefore did not meet the inclusion criteria for the study. With the sources near its half-life, the treatment time ranged from 17 minutes to 26 minutes. Dosimetrically, for the 5 patients who completed their treatment, more than 95% of the prescription dose covered the clinical target volume, and the maximum dose (D 2% ) varied from 13% to 20% of the prescription dose (see figure of sample dose distribution). With a median follow-up of 3 months, none of the patients developed treatment related toxicity. Conclusion Initial results indicate that the GammaPod system can deliver a focal dose of radiation to the breast safely. The vacuum-assisted breast cups were able to maintain the immobilization between imaging and treatment. With dynamic dose painting, the dose uniformity rivals that of external beam partial breast irradiation, but with more rapid dose fall-off outside the target, leading to substantially reduced radiation dose to the normal breast. The ability of delivering a focal dose of radiation opens the opportunity for single pre-operative irradiation as an alternative to intra-operative irradiation and pre- operative radioablation. EP-1184 HDR boost decreases the risk of breast failure in invasive breast ca. with close or involved margins J.L. Guinot 1 , M.I. Tortajada 1 , M.A. Santos 1 , F. Romero 1 , A. Moreno 2 , V. Campo 3 , L. Oliver 3 , P. Santamaria 1 , J. Fernandez 4 , L. Arribas 1 1 Fundación Instituto Valenciano de Oncologia, Department of Radiation Oncology, Valencia, Spain 2 Fundación Instituto Valenciano de Oncologia, Department of Radiation Oncology, Alcoy Alicante, Spain 3 Fundación Instituto Valenciano de Oncologia, Department of Radiation Physics, Valencia, Spain 4 Fundación Instituto Valenciano de Oncologia, Department of Radiation Oncology, Cuenca, Spain Purpose or Objective The risk of breast failure after breast-conserving treatment is two-fold higher in invasive carcinoma with positive surgical margins than in free margins, (between 12 and 34% at ten years) (1). A new resection is recommended, with risk of fair cosmetic result, or mastectomy. With close margin total dose should be higher to avoid local recurrence. Twenty years ago, we started with a high dose rate (HDR) boost after whole breast irradiation in cases with close or positive margin. We review the long-term outcome in these high risk cases Material and Methods Between 12.1996 and 12.2011, 248 patients were included, with a median age of 55 (22-90). Mean FU 127 months. By T stage 179 T1, 62 T2 and 6 T3. By margin status, 120 was positive, 76 close until 2mm, 52 close >2mm and <5mm. All of them were treated with whole breast irradiation (WBI) 50Gy plus HDR boost with 3 fractions of 4.4Gy to 85% isodose in two days, with rigid needles. The contour of CTV was decided by clinical assessment, no CT planning was used. Chemotherapy was used in 52%, and hormonal treatment in 76%. Survival was calculated by Kaplan Meyer method. Results In the whole population, actuarial breast failure at 10 and 15 years was 6.5% and 11.6%. With positive margin: 6.8% and 14.8%, with close margin ≤2mm: 9.8% and 9.8%, with

margin >2mm <5mm, 2% and 2%. By age, in 90 patients aged 50 or younger, was 11.9% and 17.8%, between 51-70, 3.8% and 8.2%, and no failures over 70. In young women under 50 with positive margin, breast recurrence was 13.1% and 24% at 10 and 15 years. By T stage, no differences between T1 and T2, no failures in T3. No differences if margin was due to invasive carcinoma or DCIS, in G3, or depending on hormonal receptors. Fibrosis or induration were registered in 26.7%, breast edema 6.5%, volume reduction 6.5%, telangiectasia 3.4%, hyperpigmentation 2.1%. Cosmetic outcome was excellent/good in 85.8%. Conclusion Long-term breast control of patients with positive or close surgical margin using WBI plus a HDR boost is similar to that achieved with free margins in the EORTC 22881-10882 trial, in all groups of age, but in young women with positive margin where a new resection is recommended. This approach is useful to avoid a second intervention, in women over 50 with positive surgical margin, or with close margins in all ages. (1) Guinot JL, et al. Breast-conservative surgery with close or positive margins: can the breast be preserved with high- dose-rate brachytherapy boost? Int J Radiat Oncol Biol Phys 2007; 68:1381-87 EP-1185 Post-operative Irradiation after Nipple- Sparing or Skin-Sparing Mastectomy: An International Survey G.N. Marta 1,2 , P. Poortmans 3 , R.A. Audisio 4 , R. Freitas Junior 5 , A.C. De Barros 6 , J.R. Filassi 7 , S.M. DeSnyder 8 , S. Meterissian 9 , T.A. Buchholz 10 , T. Hijal 11 1 Hospital Sírio-Libanês, Radiation Oncology, São Paulo, Brazil 2 Instituto do Câncer do Estado de São Paulo ICESP - Faculdade de Medicina da Universidade de São Paulo, Radiation Oncology, Sao Paulo, Brazil 3 Radboud university medical center, Radiation Oncology, Nijmegen, The Netherlands 4 University of Liverpool, Surgical Oncology, Liverpool, United Kingdom 5 Universidade Federal de Goias, Surgery, Goias, Brazil 6 Hospital Sírio-Libanês, Surgery, Sao Paulo, Brazil 7 Faculdade de Medicina da Universidade de São Paulo FMUSP, Breast Surgery Division, Sao Paulo, Brazil 8 The University of Texas MD Anderson Cancer Center, Surgical Oncology, Houston, USA 9 McGill University Health Centre, Surgery, Montreal, Canada 10 The University of Texas MD Anderson Cancer Center, Radiation Oncology, Houston, USA 11 McGill University Health Centre, Radiation Oncology, Montreal, Canada Purpose or Objective Skin sparing mastectomy (SSM) and nipple-sparing mastectomy (NSM) have entered routine surgical practice for breast cancer, though their oncologic safety has not been established in randomized controlled trials. The aim of this study was to evaluate breast surgeons’ opinions concerning the indications of post-operative radiation after SSM and NSM. Material and Methods Breast surgeons from North America, South America and Europe were invited to contribute in this study. A 22- question survey was mailed to participating breast surgeons to evaluate their opinions. the indications of post-operative radiation after SSM and NSM. Results A total of 252 breast surgeons answered the questionnaire. Most of them had at least 10 years of post-residency practice. The majority of breast surgeons affirmed that post-operative radiation should be performed in early- stage (stages I and II) breast cancer for patients who present with risk factors for relapse after SSM and