ESTRO 2020 Abstract book

S565 ESTRO 2020

overall survival and disease free survival were 97.8% (95% Confidence Interval [95% CI]: 94.1 - 99.2%), and 93.4 % (95% CI: 89.2 - 96.0%) respectively. Conclusion Early breast cancer irradiation by Tomotherapy provides low early and medium-term toxicities with good aesthetic results and quality of life; however longer follow-up is required to better assess late outcomes. PO-0975 Retrospective evaluation of clinical outcome and dosimetric aspects in breast cancer reirradiations J.A. Gomez Ramos 1 , F. Castaño 1 , J. Acosta 1 , V. Hernandez 2 , C. Aparicio 1 , E. Gomez 1 , M. Arquez 1 , L. Torres 1 , P. Araguas 1 , Y. López 1 , M. Arguís 1 , D. Gómez 1 , N. Cabré 1 , E. Rodriguez 1 , M. Arenas 1 1 Hospital Universitari Sant Joan de Reus, Department of Radiation Oncology, Reus, Spain ; 2 Hospital Universitari Sant Joan de Reus, Physics Department, Reus, Spain Purpose or Objective Locally recurrent breast cancer (LRBC) to a previously irradiated area often generates doubts about the most suitable approach for the patient. The main objective of this retrospective study is to evaluate overall survival (OS)in patients undergoing external radiotherapy for LRBC. As secondary objectives we evaluated disease-free survival (DFS) and the degree of toxicity related to dosimetric aspects and to the time elapsed since the previous Between 2010 and 2018, 30 women (mean age = 66.3 years, range: 39-86 years) were re-irradiated with external radiotherapy for LRBC, with total irradiation of the breast/thoracic wall +/- regional lymph nodes +/- boost. The following variables were studied: type of primary cancer (histology, molecular classification, grade), type of recurrent cancer (histology, molecular classification, grade), site of recurrence, radiotherapy technique, total dose, total boost dose, fraction dose, equivalent dose in 2Gy fractions (EQD2), retreatment time, type of rescue surgery, OS, DFS as well as acute and chronic dermatitis were evaluated in the present study. All statistical calculations and graph representations were performed with the statistical package for social sciences (SPSS 22.0) and the OS and DFS analysis was performed using the Kaplan-Meier method. Results Radiation therapy was administered to the breast/thoracic wall +/- regional lymph nodes +/- boost in 30 re-irradiation treatments (level I-IV nodes in 6 cases). The mean cumulativeEQD2 for the entire breast and tumor cavity (α / β = 3) was 99.1 Gy and 117.9 Gy, respectively. The mean retreatment time was 93.5 months. OS and DFS at 5 years were 88% and 63.3%, respectively. Acute dermatitis was G1-2 in 22 cases, G3 in 2 cases and G4 in 0 case. Chronic toxicity was G1-G2 in 21 cases, G3 in 4 cases and G4 in 1 case (most commonly fibrosis and telangiectasia changes, 1 case of ulceration). Patients presentingthe highest grades of acute toxicity (G3) and chronic toxicity (G3 and G4) received an EQD2 of 112,5Gy and 110Gy, respectively, although the difference in EQD2 with respect to mild toxicity cases (G1 and G2)was not statistically significant. Events of acute toxicity (G3) and chronic toxicity (G3 and G4) had a mean retreatment of 10,5 and 9,5 years respectively, although the difference in EQD2 with respect to mild toxicitycases (G1 and G2)was againnot statistically radiotherapy treatment. Material and Methods

Thirty-one (47%) of 66 patients had additional positive lymph nodes in the ALND (range one to eleven). The chance of a positive ALND increased with increasing number of positive lymph nodes on imaging prior to NAC ( P =0.010), ranging from 25.0% (one positive node) tot 69.0% (three or more positive lymph nodes). Patients with a higher pathologic tumor stage had an increased risk of additional positive lymph nodes in the ALND ( P =0.041). Conclusion The risk of finding additional positive lymph nodes in ALNDs depends on the number of positive lymph nodes before NAC and on the ypT-stage. Randomized trials are currently underway to investigate whether regional radiotherapy may provide locoregional control comparable to ALND in these patients. PO-0974 Helical intensity-modulated radiation therapy for locally advanced breast cancer:a prospective study B. Bataille 1 , F. Le Tinier 1 , R. Bennadji 1 , L. Basson 1 , A. Escande 1 , E. Tresch 2 , F. Crop 3 , F. Darloy 4 , D. Carlier 4 , X. Mirabel 1 , E. Lartigau 1 , D. Pasquier 1 1 Oscar Lambret Center, Radiation therapy, Lille, France ; 2 Oscar Lambret Center, Biostatistics, Lille, France ; 3 Oscar Lambret Center, Medical Physic, Lille, France ; 4 Leonard de Vinci Center, Radiation therapy, Dechy, France Purpose or Objective Intensity-modulated radiation therapy (IMRT) is known to provide better coverage of complex target volumes for adjuvant breast radiotherapy. It provides dosimetric advantages in order to reduce high doses delivered to organ at risk such as heart and lungs. IMRT also improves acute and late toxicity compared to conventional radiotherapy. The objective of this study is to evaluate acute and late toxicities as well as quality of life for patients treated by helical tomotherapy for locally advanced breast cancer. Material and Methods This was a prospective, routine care study, including patients treated by tomotherapy. Prescribed dose to the breast/chest wall/axillary lymph nodes was 50 Gy (25 fractions x 2 Gy) over five weeks (5 irradiations/week) with simultaneous integrated boost (SIB) at surgical bed (PTV- boost) of 60 Gy in 25 fractions (25 fractions x 2.4 Gy) after conservative treatment. The goal of the prescription was that 95% of the volume received 95% of the prescribed dose. The primary endpoint was acute and late toxicities assessed by NCI-CTCAE v4.0 scale. Secondary endpoints were quality of life using QLQ-C30 and QLQBR-23 questionnaires, aesthetic aspect of the breast after breast conserving surgery, survival (assessed by Kaplan Meier method), association between clinical or dosimetric characteristics and toxicity Results 288 patients were included from November 2014 to January 2018. 260 patients (90.3%) underwent lymph node irradiation. The median follow-up was 25 months. 278 patients (96.5%) had acute dermatitis : 172 (59.7%) grade 1, 102 (35.4%) grade 2, and 4 (1.4%) grade 3. 18 patients (6.3%) had grade 2 acute esophagitis. 86 patients (29.9%) had medium-term skin reaction, including 82 grade 1. 18 patients (6.3%) and 17 patients (10.1%) had grade ≥2 breast fibrosis and surgical bed fibrosis respectively (table 1). In multivariate analysis, smoking, D98% of supra-clavicular skin and absence of chemotherapy were associated with medium-term skin toxicity grade ≥2. The aesthetic aspect of the breast after one year was estimated "good or excellent" in 86.7% of cases according to the physician and 84.6% according to the patients. Patient’s quality of life improved over time. It concerned global health status, functional and symptomatic scale. Patients who were treated by chemotherapy before radiotherapy had poorer mean scores at the inclusion time, and most of them were significatively improved at one and six months. Two years