ESTRO 37 Abstract book

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ESTRO 37

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 Purpose or Objective To estimate the impact of molecular subtype on locoregional failure in patients treated with adjuvant radiotherapy and contemporary systemic therapy Material and Methods We retrospectively analyzed data of patients with invasive breast cancer treated with adjuvant radiotherapy at our institution between 2005 and 2015. Molecular subtypes were defined as luminal A (LA), luminal B (LB), luminal Her 2, Her 2 and triple negative (TN) based on the 2015 St. Gallen Consensus Criteria. Survival estimates were calculated according to the Kaplan-Meier method at the end of the follow-up. The association of clinicopathologic features with local failure was evaluated using Cox proportional hazards regression models. Results 870 patients were analyzed. Molecular subtypes were distributed as follows: 58.5% LA, 21.2% LB, 8.4% luminal Her-2, 3.7% Her- 2, 8.2% TN. 86% of patient underwent breast conservative surgery (BCS), 11% mastectomy. Three hundred seventy six patients (43.2%) received adjuvant chemotherapy (antracyclines 70.5% and taxanes 51.3%). The majority of patients Her 2+ (67.6%) received trastuzumab immunotherapy . Sixteen (1.8%) loco- regional relapse occurred, 12 (75%) in breast/chest wall area, 2 (12.5%) in the nodal areas, 2 in both chest wall and nodal areas (12.5%). Median follow-up was 5.1 years (range 1-12 yrs). Non LA molecular subtypes showed earlier relapse compared to luminal A subtype (median time 39 vs 75 months). The actuarial 10-year local recurrence rate was 1.6% for LA, 4.3% for LB, 11.3 for Her2 and 7.8% for TN patients (p=<0.001). Univariate Cox regression revealed several factors associated with LR : age < 50 (p=0.03), N+ (p=0.04), high histologic grade model. Results mean dose. Conclusion

(p=0.04). At multivariate analysis only high histologic grade (p=0.06) and molecular subtypes (p=0.02) were predictive of local recurrences. The 10-year metastases free survival rate of LA, LB, luminal Her2, Her2 and TN groups were 90.7, 82.4, 91.2, 90.5, 85.4% respectively (p=0.02). Conclusion Molecular phenotype has a significant impact on local and distant failure in patients with invasive breast cancer treated with radiotherapy and contemporary systemic therapy. Therefore, it should be integrated in adjuvant treatment decisions EP-1323 Dosimetry results and toxicity of a 3-week schedule RT with SIB in breast cancer, with TomoDirect M. Gerardi 1 , A. Morra 2 , S. Dicuonzo 2 , S. Arculeo 3 , F. Patti 3 , R. Ricotti 2 , V. Dell'Acqua 2 , M. Augugliaro 3 , C. Arrobbio 3 , A. Viola 3 , D. Rojas 3 , C. Fodor 2 , F. Emiro 4 , F. Cattani 4 , S. Raimondi 5 , V. Galimberti 6 , R. Orecchia 7 , M. Leonardi 2 , B. Jereczek-Fossa 8 1 Istituto Europeo di Oncologia, Radiotherapy Division, Biella, Italy 2 European Institute of Oncology, Division of Radiation Oncology, Milano, Italy 3 European Institute of Oncology and University of Milan, Division of Radiation Oncology and Department of Oncology and Hemato-oncology, Milano, Italy 4 European institute of Oncology, Unit of Medical Physics, Milano, Italy 5 European Institute of Oncology, Divisione di Epidemiologia e Biostatistica, Milano, Italy 6 European Institute of Oncology, Unità Senologia Molecolare, Milano, Italy 7 European Institute of Oncology and University of Milan, Department of Medical Imaging and Radiation Sciences and Department of Epidemiology and Statistics, Milano, Italy 8 European Institute of Oncology and University of Milan, Division of Radion Oncology and Department of Oncology and Hemato-oncology, Milano, Italy Purpose or Objective to assess toxicity and cosmetic outcome in breast cancer patients treated hypofractionated radiotherapy to the whole breast plus simultaneously concomitant boost (SIB) using TomoDirect. Material and Methods 224 patients with early breast cancer treated with breast conserving surgery were given 40.05 Gy in 15 daily fractions, 2.67 Gy per fraction to the whole breast and 48 Gy in 15 fractions, 3.2 Gy per fraction, to the tumor bed with SIB. Acute and late toxicity and cosmetic were prospectively assessed during and after radiotherapy. Results The dose distribution within the breast was the following. Regarding the breast PTV, the median volume receiving the 95% of the prescribed dose was 99.2% (range 93.5- 100), the median maximum dose (D 0.03cc ) was 118% (range 113.8-125) and median value of prescribed dose delivered to 50% of breast volume was 102% (50-106), the median value of the breast volume receiving the boost dose prescription was 0.1% (range 0-13.6). Regarding the boost PTV, the median volume receiving the 95% of the prescribed dose was 97.6 ( range 70-100), the medium maximum dose was 102% ( range 100-6- 107). Acute toxicity evaluated at the end of radiotherapy, according to RTOG scale was the following. Concerning erythema, G0 was recorded in 14% and 36%, G1 in 73% and 56%, G2 in 13% and 8% on the whole breast (WB) and on the tumor bed (TB), respectively. Concerning desquamation, G0 was observed in 91.5% and 96.4%, G1 in 6.7% and 2.7 %, G2 in 1.8% and 0.9% on the WB and TB respectively. Concerning edema, G0 was seen in 78% and 84.4% and G2 in 22% and 16% on the WB and TB,