Abstract Book

S204

ESTRO 37

2 Fundación Instituto Valenciano de Oncologia, Department of Radiation Physics, Valencia, Spain

Sweden).A single fraction of 16 Gy was prescribed on the 100% isodose.Patients were followed every 4 months during the first year, then twice a year. Oncologic outcome at 3 years was reported based on local relapse free survival (3-y LRFS), specific survival (SS) and overall survival (OS). Acute (<180 days after APBI) and late toxicity were evaluated (Common Terminology Criteria for Adverse Event v4.03).Cosmetic results were evaluated clinically by the physician. Results Between January 2012 and August 2015, 50 women (53 lesions) were treated. Median age was 77.5 (range: 65.2- 92.3) years with a median tumor size of 10 mm (range: 3- 32). Six pts presented an axillary lymph node involvement (4 Nmic, 2 N1). Invasive ductal carcinoma was the most frequent histology type (86.8%).With a median follow–up of 40months (range: 36- 43), we observed 2 local relapses (3.8%) [1 st pt: tumor size = 30 mm, security margins< 1 mm; 2 nd pt: tumor size = 20 mm, security margins < 1 mm)] and 1 axillary relapse (1.9%). The3-y LRFS, SS and OS rates were 95.3%, 100% and 93.4%. Acute toxicity occurred in 29 pts (58%) with 71 events. The most frequent acute toxicity was grade (G) 1fibrosis (45.2% of treatments),3 pts (6%) presented G3 acute toxicity (2 breast hematomas, 1 breast abscess). No ≥G3 late toxicity was observed while 15 late toxicities occurred (G1: 12 events [80%]) mainlyG1 breast fibrosis and visible puncture site scar). The rate of excellent cosmetic outcome was 75.4%. Conclusion We reported promising and encouraging clinical outcome of a post-operative single fraction of MIB ABPI in the elderly. This approach leads to consider a Hyper-APBI as an attractive alternative to intra-operative radiation therapy while 100% of the patients are good candidates for APBI in regards to the post-operative pathological report. More mature results (number of patients and follow-up) are needed. OC-0400 Eleven-Year Results Of Interstitial HDRBT APBI After BCS For Low-Risk Breast Cancer S. Kellas-Sleczka 1 , B. Bialas 1 , M. Szlag 1 , P. Wojcieszek 1 , M. Fijalkowski 1 , A. Cholewka 1 , M. Jarzab 2 , B. Lange 2 , T. Krzysztofiak 1 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Brachytherapy Department, Gliwice, Poland 2 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, III Department of Radiotherapy and Chemotherapy, Gliwice, Poland Purpose or Objective The role of APBI for patients with low-risk breast cancer has gained popularity as an alternative to the conventional whole breast irradiation (WBI) with external beam radiation. Multicatheter interstitial brachytherapy with flexible catheters located around the lumpectomy cavity is one of the oldest APBI techniques with the longest experience. The aim of the study was to report the results of 218 patients with at least 5-year follow-up treated with APBI using interstitial multicatheter high-dose-rate brachy- therapy (HDR-BT) after breast-conserving surgery. Material and Methods From July 2006 to October 2017, 443 women with low- risk invasive and ductal carcinoma in situ after BCS underwent APBI using interstitial multicatheter HDR brachytherapy at our department. In the analyzed group, 218 patients were followed up for 5 years or longer. The inclusion criteria were: ZUBROD 0 or 1, age ³50 years, T1-2N0M0, T≤3cm, unifocally, invasive carcinoma without neuroinvasion, angioinvasion, minimal surgical margin 2mm or DCIS with minimal margin at least 5mm, without EIC (extensive intraductal component), positive estrogen receptors. The time between surgery and HDR-BT was

Purpose or Objective To evaluate the influence of a high dose rate brachytherapy (HDR-BT) boost in women who showed close or positive margins after conserving surgery for Ductal Carcinoma In Situ (DCIS) of the breast. Recurrence rates have been associated with the width of the tumor- free margin and it is considered the most important predictor of local recurrence in DCIS. Material and Methods From July 1997 to February 2017, 54 women with DCIS of the breast with less than 5 mm or positive surgical margins were treated with adjuvant 50 Gy standard whole breast irradiation (WBI). Brachytherapy was performed less than 1 month from the end of EBRT. Intravenous sedation, analgesia and local anesthesia was applied to the skin at the area of entrance and exit of the needles. The contour of CTV was decided by clinical assessment, no CT planning was used. All of them were treated with high-dose-rate (HDR) brachytherapy boost with 3 fractions of 4.4Gy to 85% isodose in 24 hours, with rigid needles. Patients stayed one night in the hospital with the implantation. Median age was 61 (Range 37-79). Survival was calculated by Kaplan Meyer method. Results With a median follow-up of 91 months (range 8-240), there have been three recurrences, in postmenopausal women with positive margin. Actuarial ipsilateral breast tumor recurrence (IBTR) at 5 and 10 years was 2.4% and 13.5% in the whole group. In 22 cases with positive margin IBTR was 5.9% and 24.5% at 5 and 10%, and there were no failures in the group of 25 cases with close margin ≤2mm and 7 cases with margin >2mm <5mm (p: 0.087). No IBTR appeared in 9 women aged 50 or younger. One case of recurrence developed an invasive ductal carcinoma and bone metastasis one year later. Long-term fibrosis or induration were registered in 27.8% and telangiectasia in 1.8%. Cosmetic outcome was considered excellent or good in 93.3%. Mastectomy was the salvage treatment for the three cases of recurrence, therefore the long-term breast preservation was 94.4%. Conclusion The treatment of patients with DCIS with positive surgical margin uses to be re-exeresis, but, if rejected, there is an alternative treatment, involving WBI plus HDR-BT boost to the tumor bed. In cases of DCIS with close margin, this approach achieves a 100% of local control at ten years. OC-0399 Accelerated partial breast irradiation in the elderly: a single fraction of HDR brachytherapy R. Kinj 1 , M.E. Chand 1 , J. Gal 1 , M. Gautier 1 , L. Montagne 1 , D. Lam Cham Kee 1 , J.M. Hannoun Lévi 1 1 Centre Antoine Lacassagne, Radiation Oncology Department, Nice, France Purpose or Objective To analyze the clinical outcome of elderly women with early breast cancer who underwent accelerated partial breast irradiation (APBI) based on a post-operative single fraction of multicatheter interstitial high dose –rate A monocentric retrospective cohort study was performed focusing on elderly patients (≥65 years old) presenting a low-risk breast carcinoma treated by lumpectomy plus axillary evaluation followed by a single fraction of MIB APBI. Vectors (Sharp Needles™; Elekta AB, Stockholm, Sweden) were placed mainly intra-operativelyby the radiation oncologist using 1 to 3 planes in respect with the Paris system recommendations. A post implant-CT was performed allowing CTV delineation and dose distribution optimization (OncentraBrachy®;Elekta, brachytherapy (MIB). Material and Methods