Abstract Book

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ESTRO 37

follow-up, in 4/214 patients (2.0%) a local recurrence was found and 4/214 patients (2%) died of metastasis. Overall mortality was 5.4% and breast cancer specific mortality was 2.9%. Although the shorter follow-up, patients treated after 2010 showed a decreased local recurrence rate (early group: 4.2%; late group: 1.3%, p=0.3) and breast cancer mortality (early group: 6.3%; late group: 0.6% p=0.01). In 11.3% of cases acute side-effects were reported. The most frequent acute complications were seromas (3.3%), abscesses (2.8%) and hematomas (2.8%). 56% of cases showed at least one grade 1 or 2 late toxicity. Retractions (27%) were most commonly, pain was reported by 19.3% of the patients (grade 2 in only 1%). Patients with IORT as a boost were more likely to have late toxicity (IORT: 47.5% vs. IORT+WBI: 61.4%; p=0.08). Regarding acute and late toxicity, patients with a later treatment date had fewer complications (p=0.5; p=0.7). Conclusion Local failure, acute and long-term toxicities of the present analysis were low. Although combined therapy (IORT+WBI) seemed to be more likely to show late complications, IORT in our series confirmed to be a safe and effective treatment option, both as PBI or as anticipated boost in selected BC patients. EP-1320 Postoperative 3D-CRT for breast cancer: results from patients treated in a single institution. M. Conson 1 , L. Faraci 2 , E. Toska 2 , J. De Robbio 2 , I. Scognamiglio 2 , A. Perillo 2 , V. Agbaje 2 , M. Tirozzi 2 , A. Roscigno 2 , C. Oliviero 2 , S. Clemente 2 , L. Cella 1 , R. Pacelli 2 1 Intituto di Biostrutture e Bioimmagini, Department of Advanced Biomedical Sciences University “Federico II” School of Medicine- Napoli- Italy, Napoli, Italy 2 Department of Advanced Biomedical Sciences- University “Federico II” School of Medicine, Department of Advanced Biomedical Sciences, Napoli, Italy Purpose or Objective Outcome of postoperative radiation and possible relation with clinical factors was evaluated in breast cancer patients treated at our department. Material and Methods Eight Hundred nine consecutive breast cancer patients were postoperatively irradiated between January 1999 and December 2011. Conservative surgery was performed in 92.5%, and mastectomy in 7.5% of patients. Chemotherapy was administered to 20.5% of patients, 34.5% had hormone therapy and 45% both, while 13.4% of patients had trastuzumab. 3D-conformal radiation treatment was delivered with 50 Gy to the whole breast/chest wall (2.0 Gy/25 fractions). In the case of conservative surgery a boost dose of 10 Gy in 5 days was delivered by electrons on the tumoral bed. When appropriate, nodal irradiation (2.0 Gy/25 fractions) was performed. Local, regional and distant relapse together with contralateral breast cancer and second tumors were considered as outcome. Clinical variables such as age, stage, tumor size, nodal status (number of positive nodes, nodal ratio), hormonal receptor status, c-erbB2 expression, Ki67, approximate genetic signature were considered in relation to clinical outcome. Results At diagnosis 5.9% of patients was at stage 0, 47.4% stage I, 34.9% stage II and 11.8% stage III. Median age was 55 (27-83), and median follow up resulted to be 81 months (3 – 219). Survival rate was 94.7%. Local, regional and distant relapses were 3.3%, 2.1% and 6.3%, respectively. The rates of contralateral breast cancer and of second tumors were 1.1% and 3.1%, respectively. With regard to local recurrence rate, stage did not have a significant impact. As expected, stage 0 patients (DCIS) showed a trend toward a higher recurrence risk when compared with stage I-III patients (8.7% vs 3.4%, p=0.06). Distant recurrence rate was significantly related to disease stage

(p<0.01), as to as Ki67 level. Among node positive patients, a worse distant relapse rate was significantly correlated with a higher number of positive nodes and higher nodal ratio (p<0.05). Conclusion Outcome of breast cancer patients treated with modern radiotherapy is good. Radiotherapy seems to flat the risk of local relapse linked to the disease stage. Stage, Ki67, number of involved nodes, and ratio involved/removed nodes resulted significantly related to distant relapse in our series. EP-1321 Incidental radiation dose to the Internal mammary chain in a large clinical breast series G. Loganadane 1,2 , B.H. Kann 1 , M.R. Young 1 , C.A. Knowlton 1 , S.B. Evans 1 , S.A. Higgins 1 , Y. Belkacemi 2 , L.D. Wilson 1 , M.S. Moran 1 1 Yale University School of Medicine, Department of Therapeutic Radiology, New Haven- Connecticut, USA 2 APHP.University of Paris-Est Creteil UPEC, Department of radiation oncology & Henri Mondor Breast Center, Créteil Cedex, France Purpose or Objective To evaluate the incidental dose to the internal mammary nodes (IMN) in patients treated with three dimensional conformal radiation therapy (3D CRT) and identify potential parameters that may impact the IMN mean dose. Material and Methods Our study cohort included 362 breast cancer (BC) patients treated between January 2015 and July 2017. patients received loco-regional irradiation as a part of their definitive BC therapy. Patients were treated with standard 3D field-in-field techniques without intentional inclusion of the IMN chain. The primary endpoint was to assess the mean dose to the IMN chain (as defined by the RTOG Breast Atlas definition) normalized to the prescribed dose with treatment of a tangential breast or chest wall fields. IMN chain was contoured to anatomically identify the upper, mid, and the lower-third of the internal mammary chain, and potential parameters influencing IMN mean dose to these regions were analyzed using a linear regression The IMN mean dose was 36% +/- (standard deviation; SD) 28.7%. The Kruskall-Wallis test demonstrated significant differences in median dose levels in the 3 sub-regions: upper (7.2%), mid (21.5%) and lower (41.7%), p<0.001. Pre-sternal fat thickness (regression coefficient; RC): - 16.4, p<0.001 ), post-mastectomy radiation (RC; 24 , p<0.001), reconstruction after mastectomy (RC;-22.4, p<0.001 ) and the addition of a 3 rd (supraclavicular) field (RC; 8.8, p=0.03) were significantly associated with IMN Unlike the axilla level I and II, which has been shown to incidentally receive therapeutic doses in a significant proportion of patients undergoing standard tangential fields, the IMN chain does not appear to be adequately covered in most cases. Therefore, if comprehensive regional nodal radiation to include the IMNs is indicated, the contouring of this nodal chain and specification of its inclusion in the radiation prescription is warranted. EP-1322 Patterns of failure according to breast cancer subtype after RT and contemporary systemic therapy. E. Ippolito 1 , S. Silipigni 1 , A. Di Donato 1 , G. Petrianni 1 , P. Matteucci 1 , E. Molfese 1 , A. Sicilia 1 , L. Trodella 1 , R. D'Angellillo 1 , S. Ramella 1 1 Campus Biomedico University, Radiotherapy, Roma, Italy model. Results mean dose. Conclusion