ESTRO 2021 Abstract Book

S928

ESTRO 2021

Conclusion Based on these dosimetric parameters we can conclude that although Tomotherapy could achieve excellent target coverage, conformal dose distribution and significantly reduce the ipsilateral breast dose exposure, this was at the expense of very high OAR doses. Meanwhile 3DCRT provided comparable target volume coverage coupled with superior OAR sparing. Larger prospective clinical series are needed to study the long term outcomes of both techniques in this patient population. PO-1114 “One minute” IORT for low-risk breast cancer: feasibility, reproducibility and early toxicity report M. Chand-Fouché 1 , C. Colnard 1 , D. Lam Cham kee 1 , J. Gal 2 , C. Dejean 1 , M. Gautier 1 , J. Feuillade 1 , A. Mana 1 , Y. Fouché 3 , Y. Delpech 3 , M. Dejode 4 , J. Gérard 1 , E. Barranger 1 , J. Hannoun-Levi 1 1 Centre Antoine Lacassagne, Radiation Oncology, NICE, France; 2 Centre Antoine Lacassagne, Biostatistics, NICE, France; 3 Centre Antoine Lacassagne, Breast surgery, NICE, France; 4 Centre Antoine Lacassagne, Breast Surgery, NICE, France Purpose or Objective Since then, intra operative radiation therapy lengthened operating time by 30 minutes. A phase 2 study was conducted with Papillon+ TM Contact X-ray machine designed to produce a 50 kVp high-dose rate of 20-30 Gy/minute. Materials and Methods Patients ≥ 60 years, with low-risk ductal breast adenocarcinoma ≤ 2.5 cm, had breast conservative surgery and 20 Gy intra operative radiation therapy (IORT). The primary end point was feasibility/reproducibility based on the doses measured with the Gafchromic films. Early toxicity was also investigated. Results Between 10/2018 and 09/2019, 26 patients were included. Median age was 73 years [range 61 – 90]. Median treatment time was 49 seconds [range 40 – 112]. Mean Gafchromic doses were 18.8 Gy (± 2 Gy) , 15.6 Gy (± 2.81 Gy) and 2.5 Gy (± 1.67 Gy) at the south pole, the equator and the skin respectively. Two patients received postoperative irradiation to the whole breast and regional nodes. With a median follow-up time of 12 months [range 10 -22], acute toxicity was observed for 6 patients : 2 erythema grade 1, 1 seroma grade 1, 3 hematomas grade 2. Chronic toxicities were 1 telangiectasia grade 1, 1 hyperpigmentation grade 1, 6 fibrosis ≤ grade 2. Patient satisfaction was estimated good to excellent in 24 cases. Conclusion This is the first phase 2 study testing the Papillon+ TM system, able to deliver 20 Gy IORT in one minute for patients above 60 years and low-risk breast cancer, with important in-vivo dosimetry measurements and encouraging early toxicity data. PO-1115 Extreme weekly locoregional hypofractionated radiation in elderly with non-metastatic breast cancer F. Rais 1 , J.M.G. Tsui 1 , M.D. Faye 1 , A. Daianska 1 , C. Lambert 1 , M. David 1 , V. Panet-Raymond 1 , M. Azoulay 1 , A. Saidi 1 , T. Hijal 1 1 McGill University Health Centre, Cedars Cancer Centre., Radiation-oncology, Montreal, Canada Purpose or Objective Breast cancer locoregional (LR) radiation in the elderly requires careful consideration between the benefits of aggressive treatment and its potential toll on elderly patients. Extreme weekly LR hypofractionated radiation (HFRT), defined as a fractionation regimen delivering more than 5 Gy per fraction, given weekly, is a treatment option that may be better suited in such a population. It represents a good compromise between omitting and exhaustive daily radiation over several weeks, especially in frail and elderly women. It is also a less cumbersome therapeutic alternative that would offer similar efficacy with comparable or lower toxicity rates. This study aims to report the local and LR control rate as well as the acute and long-term side effects of the elderly patients treated with HFRT in our institution, and to compare these results to those from the literature. Materials and Methods We conducted a retrospective study by reviewing medical records of elderly patients with breast cancer treated with adjuvant once-weekly LR HFRT in our institution between 2011 and 2020. Fifty patients presenting with primary non-metastatic breast tumors (Stage I–III) were included. Treatment outcomes including local/LR control, distant metastasis, cause-specific survival, and overall survival were reported. Early and late toxicity profiles were also assessed. Results