ESTRO 38 Abstract book

S720 ESTRO 38

divided into two groups according to tumour laterality. All patients were treated on linear accelerator with 3- dimensional conformal RT technique, following our protocols: whole breast to a total dose of 50 Gy in 2 Gy fractions or 40.05-42.72 Gy in 15-16 fractions and a tumour bed boost of 16 Gy in 8 fractions, if indicated. The heart, LAD, and LV were contoured retrospectively, according to RTOG guidelines. For each patient, the MHD and dose-distribution parameters of the LAD and LV were extracted from our treatment planning system. Differences were analyzed with two-tailed two-sample unpaired Mann-Whitney U-test (α=0.05). Results The study cohort consisted of 117 patients (68 left(L)- sided and 49 right(R)-sided breast cancers) who had been treated in our institution. For analysis, the sample was divided into two groups according to tumour laterality. 89% were breast conserving patients. 33 patients received radiation on their axillary and/or supraclavicular nodes. Table 1 details clinical and dosimetric characteristics of the population according to the fractionation schedule. For the entire cohort of L-sided patients, the MHD was higher compared to R-sided patients: 5.75 Gy (3.52; 7.4) and 1.25 Gy (1.07;1.5), p< 0.005, respectively. The mean dose to LAD was 26.4 Gy (9.6; 34.06) for L breast sided patients and 0.95 Gy (0.79;1.13) for R breast sided patients, p<0.005. The mean dose to the LV was 9.84 Gy (5.88;12.53) for L-sided patients compared to 0.72 Gy (0.64;0.89) for R-sided patients, p<0.005. For L-sided patients a significant correlation was found between the MHD and the mean dose to the LAD, as shown in Fig.1. For every 1 Gy increase in MHD, mean LAD dose increased by 4.26 Gy. The MHD with the mean LV dose was also correlated (fig.1). A correlation between the dose to the LV and LAD was also demonstrated so that for every 1 Gy increase in mean dose to LV, mean LAD dose increased by 2.4 Gy (95% CI 2.08; 2.76) p<0.001. In addition, a correlation between these dosimetric parameters was demonstrated in R-sided patients (Fig2).

Japan ; 2 Teikyo University Hospital, Radiology, Tokyo, Japan ; 3 National Institute of Radiological Sciences, Research Center Hospital for Charged Particle Therapy, Chiba, Japan ; 4 St. Luke’s International Hospital, Radiation Oncology, Tokyo, Japan Purpose or Objective Primary squamous cell carcinoma (SqCC) of the breast is a rare disease comprising only 0.1% of all breast cancer. Because of its rarity, the standard therapy for the breast SqCC has not been established, and the role of adjuvant We conducted a multicenter retrospective cohort study in four hospitals. Patients diagnosed with primary breast SqCC who received adjuvant radiotherapy as part of primary definitive treatment were included. Patients received radiotherapy for recurrence or palliative setting were excluded. Clinical outcome and the types of recurrence were examined. Overall survival (OS) and progression-free survival (PFS) were calculated using the Kaplan-Meier method. Results From January 2002 to December 2017, seventeen breast SqCC patients who received adjuvant radiotherapy were included in the analysis. Median follow-up time was 33 months (range; 9-157). Median age was 54 years (range; 29-83). Two (12%), twelve (71%) and three (18%) patients had clinical stage I, II and III disease, respectively. Eleven (65%) patients underwent lumpectomy and subsequently had adjuvant radiotherapy to the conserved breast. Six (35%) underwent mastectomy and had post-mastectomy radiotherapy; five patients to the chest wall and regional lymph nodes and one patient to the chest wall only. Twelve (71%) had neo/adjuvant chemotherapy. Three (18%), ten (59%) and four (24%) patients had pathological stage I, II and III disease, respectively. Five (29%) had ER(+), two (12%) had PR(+) whereas none had HER2 overexpression. Twelve patients had triple negative breast cancer. Four patients (24%), 3 clinical stage II and 1 clinical stage III, had disease recurrence with a median progression-free interval of 292 days. The first site of recurrence was locoregional in 3 and concurrent local and distant metastasis in one. Two local recurrences occurred within the irradiated field. Five patients (37%) died, and four were due to breast cancer. Three-year OS rate was 69%, and three-year PFS rate was 73%. Conclusion Breast SqCC carries a high risk of recurrence and worse prognosis. Multidisciplinary treatment may be required to prevent a recurrence, and further research is needed to clarify the best treatment approach. EP-1314 Cardiac structures doses and correlation with mean heart dose in breast radiotherapy treatment M. Vázquez 1 , A. Giraldo 1 , S. Micó 1 , M. Altabas 1 , D. Sánchez 2 , J. Giralt 1 , V.M. Reyes Lopez 1 1 Hospital Universitario Vall d'Hebron, Radiation Oncology, Barcelona, Spain ; 2 Hospital Universitario Vall d'Hebron, Physics Department, Barcelona, Spain Purpose or Objective Several authors have related the late cardiac toxicity in breast cancer (BC) patients to dosimetric parameters such as mean heart dose (MHD), and dose to left anterior descending artery (LAD) and the left ventricle (LV). Due to the difficulty in contouring these structures, we evaluated whether there was a significant correlation between the MHD and different parameters over LAD and LV. Material and Methods We analysed female patients with BC treated with adjuvant Radiotherapy (RT) from January 2010 to December 2010 in our institution. Patients with previous thoracic RT were excluded. For analysis, the sample was radiotherapy is unclear. Material and Methods