ESTRO 38 Abstract book

S702 ESTRO 38

BCa pts treated with 3DCRT after breast conserving surgery were considered: 50Gy (2Gy/fr) whole breast photon RT followed in some cases by 10 or 16Gy photon or electron boost to the tumour bed. Acute skin erythema (AE) was assessed using RTOG scoring system before RT and every 5 fractions. Grade 2+ AE before boost was considered as the primary endpoint. Relevant clinical risk factors were prospectively recorded, dosimetric features were extracted from skin dose-volume histogram, with skin defined as the difference between the body contour and a 5mm inner isotropic contour from the body. Peripheral blood was obtained, RNA extracted from mononuclear lymphocytes (after in vitro expansion) and GEP determined using Illumina HumanHT-12 v4 Expression BeadChip (≈47000 probes, ≈37000 genes). Unsupervised clustering was used to reduce the dimensionality of data (partition around medoids). Dosimetric, clinical and genetic variables were included into logistic regression. Results 147 pts were available, 35/147 (24%) pts with grade2+ AE before boost, 82/147 pts had GEP information. Unsupervised clustering selected 208 genes identifying 3 clusters of pts: 38% toxicity in cluster A, 19% and 14% in clusters B and C, respectively (OR=5 for A vs “B OR C”, p=0.01). Cluster A was mainly characterized by underexpression of genes involved in immunoregulation, inflammatory processes, antioxidant activity, cell cycle progression and differentiation. Multivariable regression resulted in a 3 variable clinical/dosimetric/genetic model including dose to 20cc of skin (p=0.02, OR=1.4 for 1Gy increase), skin phototype (p=0.05, OR=1.9 1+2 vs >2), GEP cluster (p=0.01, OR=5 A vs B+C). Inclusion of GEP clustering improved likelihood (-86.6 vs -78.9, p=0.05), calibration slope (0.86 and R 2 =0.01 vs 0.93 and AUC (0.62 vs 0.83, p=0.01). The figure shows details on study population, GEP clustering and predictive model curves. Conclusion Gene expression profiling resulted in the identification of a signature of enhanced radiosensitivity for acute toxicity after BCa RT. This signature was included in a predictive model leading to significant improvement in calibration, likelihood and discrimination. EP-1281 New aspects regarding the treatment of multicentric compared to unifocal breast cancer C. Matuschek 1 , B. Tamaskovics 1 , W. Budach 1 , J. Haussmann 1 , E. Boelke 1 , F. Djiepmo 1 , T. Fehm 2 , E. Ruckhaeberle 2 , M. Fleisch 2 , S. Roth 1 1 University Hospital Düsseldorf, Radiation Oncology, Düsseldorf, Germany ; 2 University Hospital Düsseldorf, Gynecology, Düsseldorf, Germany Purpose or Objective This study compares retrospectively from 1991-1998 the Overall survival (OS), five year disease related survival (DRS), relapse free and overall survival (RFS) in multicentric breast cancer compared to unifocal breast cancer. Material and Methods From our cohort including n=482 patients n= 85 (17,6%) presented with multicentric and 397 with unicentric breast cancer. 45% of the 85 multicentric patients and 34% of the 397 unicentric patients were ≤50 years. N=254 patients received breast conserving therapy and n=228 underwent mastectomy. 392 patients received chemotherapy and in n=90 patients no chemotherapy was administered. In the multicentric group n=74 received chemotherapy and n=11 not. N=383 patients were irradiated (n=56 in the multicentric group) and n=99 patients were not irradiated (n=29 in the multicentric

Center for Proton Therapy, Goyang, Korea Republic of ; 5 Yonsei Cancer Center, Department of Radiation Oncology, Seoul, Korea Republic of ; 6 Samsung Medical Center, Department of Radiation Oncology, Seoul, Korea Republic of ; 7 Dongsan Medical Center, Department of Radiation Oncology, Daegu, Korea Republic of Purpose or Objective To analyze the treatment outcomes of ipsilateral cervical lymph node (LN)-positive breast cancer in the absence of other distant metastases, and to compare these outcomes with those of supraclavicular LN (SCL)-positive breast cancer. Material and Methods Seventy-nine breast cancer patients with involvement of ipsilateral cervical LN above the supraclavicular fossa (cervical LN(+) group) were treated with curative intent from 2000 to 2014 at 7 institutions. Most patients (n=75) received systemic chemotherapy (neoadjuvant and/or adjuvant) and breast surgery followed by locoregional radiotherapy. Outcomes of the cervical LN(+) group were evaluated and compared with those of 183 patients with SCL involvement (SCL(+) group) from the KROG 16-14 study. Results Median follow-up duration was 51.2 months (range, 5.9- 138.0). Twenty-two regional failures were found in 15 patients: axillary LN in 8, SCL in 6, internal mammary LN in 3, involved cervical LN in 4, and uninvolved cervical LN in 1. The 5-year overall survival (OS), disease-free survival (DFS), locoregional relapse-free survival (LRRFS), and distant metastasis-free survival (DMFS) rates were 64.9%, 44.8%, 68.9%, and 55.2%, respectively. Neck dissection failed to improve LRRFS and DFS (p=0.901 and 0.366, respectively). After propensity score matching, survival outcomes of the cervical LN(+) and SCL(+) groups were not statistically different (5-year OS, 62.6% vs. 72.2%, p=0.560; DFS, 45.7% vs. 52.2%, p=0.620; LRRFS, 64.7% vs. 78.1%, p=0.110; DMFS, 57.4% vs. 53.2%, p=0.590, respectively). Conclusion Based on comparable clinical outcomes, breast cancer patients with ipsilateral cervical LN metastases without other distant metastases might benefit from aggressive locoregional and systemic treatments as those with N3c disease. EP-1280 Identification of gene profiles associated to increased risk of acute toxicity in breast cancer M.C. De Santis 1 , I. Salido 2 , P. Gandellini 3 , A. Cicchetti 4 , T. Rancati 4 , M. Dispinzieri 5 , M. Carrara 6 , T. Giandini 6 , E. Pignoli 6 , E. La Rocca 5 , N. Zaffaroni 2 , R. Valdagni 7 , L. Lozza 8 1 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy Department, Milan, Italy ; 2 Fondazione IRCCS Istituto Nazionale dei Tumori, Molecular Pharmacology, Milan, Italy ; 3 Fondazione IRCCS Istituto Nazionale dei Tumori, Molecular Pharmacology-, Milan, Italy ; 4 Fondazione IRCCS Istituto Nazionale dei Tumori, Prostate Cancer Program, Milan, Italy ; 5 Fondazione IRCCS Istituto Nazionale dei Tumori- Milan University, Radiotherapy Unit 1- Oncology and Hemato-Oncology University, Milan, Italy ; 6 Fondazione IRCCS Istituto Nazionale dei Tumori, Medical Physics, Milan, Italy ; 7 Milan University- Fondazione I.R.C.C.S Istituto nazionale Tumori, Radiotherapy Unit 1- Prostate Cancer Program- Oncology and Hemato-Oncology University, Milan, Italy ; 8 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy Unit 1, Milan, Italy Purpose or Objective To identify gene expression profiles (GEP) associated to increased risk of grade 2+ acute skin erythema after adjuvant breast cancer (BCa) radiotherapy (RT). Material and Methods

group). Results

The five-year OS in the multicentric group was: 78.5%, the RFS was: 75.1%, DRS: 91.8%., compared to the unicentric group: OS: 91.8%, RFS: 91.1%, DRS: 96.1%. In the 85