ESTRO 38 Abstract book

S712 ESTRO 38

EP-1300 Beware of IMRT axillary dose reduction in non- axillary-dissected breast cancer patients J. Gadea 1 , I. Ortiz 1 , D. Morera 2 , F. Sansaloni 2 , R. Roncero 1 , M. Hernández 2 , L. Valencia 1 , M.J. Sánchez 2 , J.E. Maturana 1 , J. Font 2 , P. José 1 1 Hospital Universitari Son Espases, Radiation Oncology, Palma de Mallorca, Spain ; 2 Hospital Universitari Son Espases, Medical Physics, Palma de Mallorca, Spain Purpose or Objective Classically the standard radiotherapy (RT) treatment in breast cancer has been tridimensional conformal radiotherapy (3D-CRT) with two tangential fields. In the IMRT era, homogeneity and conformity of the dose and target coverage has been improved in RT treatments. However, this fact could minimize the incidental irradiation of the axilla with potential clinical consequences. The aim of this study is to compare incidental axillary dose in breast cancer patients treated Twenty female patients with breast cancer treated with breast-conserving surgery and adjuvant hypofractionated RT were evaluated in this study. Two dose groups were made for the analysis, one no-boost and one boost group for each patient. The total prescribed dose in the boost group was 40.05 Gy in 15 fractions (fx) to the whole breast and a 13.35 Gy/5fx photon boost to tumor bed sequentially in the 3D-CRT treatment and 40.05 Gy in 15fx to the whole breast and a 48 Gy/15fx photon integrated boost in the IMRT treatment. The total prescribed dose in the no-boost group was 40.05 Gy in 15fx for both techniques. Treatment plans were evaluated using cumulative dose–volume histogram data. Breast tissue, axillar node levels I, II and III and Rotter nodes and a sum of all were delineated. For the statistical analysis a T- student test was performed. Results In the no-boost group, IMRT technique showed significantly lower axillary irradiation compared with 3D- CRT (D mean for total axilla: 23.84±6.57 Gy vs 30.53±8.44 Gy, p<0.05) (Image 1). In the boost group, IMRT also showed significantly lower axillary irradiation compared with 3D-CRT (D mean for total axilla: 25.34±7.07 Gy vs 31.23±8.80 Gy, p<0.05). However, the boost location (upper quadrants vs lower quadrants) did not cause statistically significant differences in axillary dose with any of the two techniques. Details of each axillary level are shown in Table 1. When differences between the boost group and no-boost group treated with IMRT were evaluated, a significantly lower axillary irradiation was observed in the no-boost group (D mean for total axilla: 25.34±7.07 Gy vs 23.84±6.56 Gy, p<0.05). In contrast, although this difference was also seen with 3D-CRT between both groups, it was not statistically significant. with IMRT vs 3D-CRT. Material and Methods

Conclusion Incidental irradiation of the axilla was significantly lower with IMRT compared to 3D-CRT. Therefore, IMRT should be cautiously used in patients with limited positive sentinel lymph node disease who undergo breast conserving treatment without complete axillary lymph node dissection. There is a risk of leaving untreated microscopic node disease in these patients if we do not include axillary levels in the target volume. EP-1301 Postoperative EBRT in breast cancer: an analysis on 768 patients about predictors of late toxicity A. Zamagni 1 , M. Buwenge 1 , M. Ferioli 1 , S. Bisello 1 , I. Capocaccia 1 , I. Ammendolia 1 , G. Macchia 2 , F. Deodato 2 , M. Boccardi 2 , D. Smaniotto 3 , S. Cilla 4 , A. Ianiro 4 , A. Di Stefano 5 , E. Cucci 6 , G.P. Frezza 7 , A.G. Morganti 1 , S. Cammelli 1 1 University of Bologna- Sant'Orsola-Malpighi Hospital, Radiation Oncology Center- Department of Experimental- Diagnostic and Specialty Medicine – DIMES, Bologna, Italy ; 2 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Radiotherapy Unit, Campobasso, Italy ; 3 Policlinico Universitario “A. Gemelli”- Università Cattolica del Sacro Cuore, Department of Radiotherapy, Roma, Italy ; 4 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Medical Physics Unit, Campobasso, Italy ; 5 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Gynecologic Oncology Unit, Campobasso, Italy ; 6 Fondazione di Ricerca e Cura “Giovanni Paolo II”, Radiology Unit, Campobasso, Italy ; 7 Bellaria Hospital, Radiation Oncology Unit, Bologna, Italy Purpose or Objective To retrospectively evaluate risk factors for skin and subcutaneous late toxicity in 768 patients (pts) conservatively treated for breast cancer. Material and Methods We analysed 5-year G ≥ 2 skin and subcutaneous late toxicity-free survival (LTFS) stratifying pts based on potential risk factors: hypertension, diabetes, smoking habit, alcohol consumption, chemotherapy, hormonotherapy, stage, PTV volume, and EQD2. Results Univariate analysis results are shown in table 1. No correlation was found between G ≥ 2 LTFS and diabetes, smoking habit and alcohol consumption. Small but statistically significant correlations were found between