ESTRO 37 Abstract book

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ESTRO 37

and TN, respectively. OS was significantly shorter in the TN cohort, instead of HER2 group probably due to targeted therapies. Conclusion SRT provides a good local control on brain metastases in patients affected by BC. In this analysis molecular subtypes are not predictive of response to SRT. EP-1326 Hypofractionated IMRT using Tomotherapy for early stage breast cancer: early chronic toxicity S. Dicuonzo 1 , S. Raimondi 2 , A. Surgo 3 , R. Spoto 3 , M. Gerardi 3 , A. Morra 3 , R. Ricotti 3 , V. Dell'acqua 3 , A. Casbarra 4 , S. Arculeo 4 , D. Rojas 4 , R. Luraschi 5 , F. Cattani 5 , C. Fodor 2 , P. Veronesi 6 , R. Orecchia 7 , M. Leonardi 3 , B. Jereczek 4 1 Dicuonzo Samantha, European Institute of Oncology, Milan, Italy 2 European Institute of Oncology, Department of Epidemiology and Biostatistics, milan, Italy 3 European Institute of Oncology, Department of Radiation Oncology, milan, Italy 4 European Institute of Oncology and University of Milan, Department of Radiation Oncology and Department of Oncology and Hemato-oncology, milan, Italy 5 European Institute of Oncology, Unit of Medical Physics, milan, Italy 6 European Institute of Oncology, Department of Surgery, milan, Italy 7 European Institute of Oncology and University of Milan, Department of Medical Imaging and Radiation Sciences and Department of Oncology and Hemato-oncology, milan, Italy Purpose or Objective to present two-years toxicity and cosmesis for breast cancer patients treated with a hypofractionated scheme including simultaneously integrated boost (SIB) using TomoDirect Material and Methods Two hundred and fifty women with Tis-T2 N0-N1 invasive breast cancer operated on conservatively were treated with hypofractionated scheme using TomoTherapy with Direct modality. Whole breast (WB) radiation and tumor bed (TB) were treated simultaneously to a dose of 45 Gy and 50 Gy, respectively, in twenty fractions over four weeks. Late toxicity was evaluated according to LENT/SOMA scale. Cosmesis was evaluated both by physicians and patients using a four-point scale according to Harvard criteria. Results Median age was 53 years (26-85). Median breast and tumor bed volume were 523 cc (85-2161) and 26 cc (2- 142) respectively. Most patients received quadrantectomy + sentinel node biopsy (70%). Median follow-up was 23.91 months (interquartile range: 17.66- 26.09). Planning target volume (PTV) coverage and healthy tissues sparing were satisfactory. Median value of V95% was 100% and 99% for PTV WB and PTV TB , respectively. Median maximum dose to PTV WB and PTV TB were 113% and 103%, respectively. The table presents the highest grade of toxicities reported at the last follow-up. Neither grade 4 skin ulceration nor soft tissue necrosis was observed. Grade 3 toxicity was very limited. At univariate analysis, predictor for any severe toxicity (LENT/SOMA grade ≥2) was breast volume only ( p<0.001), while tumor bed volume showed a trend ( p= 0.06). Statistically significant relationship between age and any grade late toxicity was also found. Cosmetic outcome was categorized into excellent/good (89% for physicians and 83% for patients) and fair/poor. However, patient and physician-rated cosmesis showed poor agreement [weighted Kappa of agreement =0.50 (95% CI,0.41-0.59)].

Conclusion although larger breast volume correlated with increased severe toxicity, Grade ≥ 2 toxicity was mild and acceptable. Cosmesis was mostly rated as excellent/good. These promising results must be confirmed with a longer follow-up. EP-1327 Risk of relapse according to molecular subtype in patients with 1-3 positive nodes after adjuvant RT A. Di Donato 1 , S. Silipigni 1 , E. Ippolito 1 , G.M. Petrianni 1 , C.G. Rinaldi 1 , A. Iurato 1 , B. Santo 1 , P. Trecca 1 , R.M. D'Angelillo 1 , L. Trodella 1 , S. Ramella 1 1 Campus Biomedico University, Radiotherapy, Roma, Italy Purpose or Objective To evaluate the impact of molecular subtype on locoregional failure in breast cancer patients with 1-3 positive nodes after postoperative radiotherapy. Material and Methods From an institutional database we identified 321 patients with 1-3 positive nodes treated with postoperative radiotherapy from 2005 to 2016. 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. Kaplan Meier log-rank and Cox-regression multivariate analysis were performed to evaluate the relationship between molecular subtypes and locoregional recurrence. Results Median follow-up was 4.2 years (range 1-12 yrs). Molecular subtypes were distributed as follows: 57.6% LA, 24.9% LB, 8.7% luminal Her-2, 1.9% Her- 2, 6.8% TN. Two hundred seventy (83.1%) patients underwent breast conserving surgery and fifty-five (16.9%) received mastectomy. All patients received adjuvant radiotherapy to whole breast or chest wall. Sixty-four (19.7%) patients received also radiotherapy to supra-infraclavicular nodes. Luminal A subtype had lowest histologic grades (p=<0.001), lowest extracapsular spread rate (p=0.03). Four (1.24%) loco-regional relapse occurred, 2 (50%) in breast and 2 (50%) in the chest wall area. No difference in local recurrence rate was observed according to molecular subtypes, irradiation of supra-infraclavicular nodes, age, tumor diameter (p=NS). Only the number of positive nodes (1 vs 2-3) was associated with local recurrence risk (p=0.017). Luminal A subtypes had a 10 years metastasis free survival rate higher compared to other subtypes (86.9% vs 64.6%; p=<0.001). Conclusion The loco-regional recurrence rate observed was very low. Postoperative radiotherapy even if not associated with supra-infraclavicular nodal irradiation seem to be