ESTRO 2020 Abstract Book

S88 ESTRO 2020

Results We identified eleven studies (n=15555 patients) randomizing between PBI and WBI. IBTR was not significantly different between the groups (HR=1.25; CI95%:0.91-1.72; p=0.171). A higher rate of IBTR was dependent on PBI technique and localization of the recurrence in the breast. We did not find any differences in OS (HR=1.00; CI95%:0.85-1.18; p=0.958) and BCSS (HR=1.05; CI95%:0.74-1.49; p=0.772). However PBI resulted in a significant decrease in non-breast cancer death (NBCD) (OR=0.73; CI95%:0.56-0.96; p=0.023). DFS was superior in the WBI arm (OR=1.16; CI95%:1.04-1.29; p=0.007). Any acute side effects were reduced after PBI. Cosmetic outcome and late toxicities were inferior in accelerated external beam PBI schedules. Conclusion Limiting the target volume to partial breast radiotherapy appears to be appropriate for some patients with breast cancer. The benefit of WBI seems to be highest in patients with higher risk for ipsilateral in-breast and regional recurrences. Additionally, PBI seems to lower the risk of NBCD. Cosmetic results and adverse events are dependent on techniques and treatment schedules. PD-0180 Interim Report from the SAVE HEART Study: deep inspiration breath-hold in left-sided breast cancer S. Schönecker 1 , A. Gaasch 1 , M. Pazos 1 , D. Reitz 1 , M. Braun 2 , N. Harbeck 3 , P. Freislederer 1 , M. Niyazi 1 , C. Belka 1 , S. Corradini 1 1 LMU Munich, Department of Radiation Oncology, Munich, Germany ; 2 Red Cross Hospital, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany ; 3 LMU Munich, Department of Obstetrics and Gynecology- Breast Centre, Munich, Germany Purpose or Objective SAVE-HEART is a prospective study of left-sided breast irradiation in deep inspiration breath-hold (DIBH) with a focus on the cardiac baseline risk of individual patients and the dosimetric benefit of DIBH. The study is registered in the German Register for Clinical Studies under the study number DRKS00011213. We report below on the dosimetric evaluations. Material and Methods Inclusion criteria were a histologically confirmed left-sided invasive breast carcinoma or carcinoma in situ after breast conserving surgery (BCS) or mastectomy with indication for adjuvant radiotherapy of the residual breast/thoracic wall ± locoregional lymph drainage pathways, as well as the ability to hold breath for at least 20 seconds. Hypofractionation (40.05 Gy in 15 fractions) or boost irradiation were permitted. To date, 322 patients have been included in this evaluation and were treated within the study. The deep inspiration irradiation was applied using the automatically gated Catalyst TM /Sentinel TM system (C-RAD AB, Uppsala, Sweden) with audio- and WLAN- glasses-based video feedback. CT and surface data were acquired both in DIBH and in free breathing (FB). Results 129 of 322 patients were irradiated with normofractionation. For these patients, the mean heart dose could be reduced by -36.12 % (2.83 to 1.81 Gy) by DIBH. The maximum dose of the heart and LAD (left anterior descending artery) was reduced by -35.96 % (43.86 to 28.09 Gy) and -53.63 % (32.89 to 15.25 Gy), respectively. For the 193 hypofractionated irradiated patients, the following reductions resulted from deep inspiration: mean heart dose -34.85 % (1.96 Gy to 1.28 Gy); maximum dose heart -41.80 % (34.27 Gy to 19.95 Gy), maximum dose LAD -54.79 % (24.27 Gy to 10.97 Gy). All values described here were significant for a significance

patients with indication for radiation should be screened for a therapy in deep inspiration and treated accordingly. PD-0181 Relationship between low dose to heart substructures and heart damage within SAFE trial (NCT2236806) I. Desideri 1 , G. Francolini 1 , I. Meattini 1 , L. Dominici 1 , S. Lucidi 1 , V. Maragna 1 , V. Salvestrini 1 , E. Scoccimarro 1 , G. Stocchi 1 , M.A. Teriaca 1 , G.A. Barletta 2 , L. Livi 1 1 University of Florence, Radiotherapy Department- Careggi Hospital, Firenze, Italy ; 2 University of Florence, Cardiology Department- Careggi Hospital, Firenze, Italy Purpose or Objective Adjuvant radiotherapy may increase risk of cardiovascular comorbidity in breast cancer patients, especially if left sided. However, no threshold dose has been evidenced in literature, and no data about heart substructures have been collected so far. Patients undergoing adjuvant treatment for breast cancer in our institute are included in a study protocol aimed to reduce cardiovascular morbidity and based on periodic follow up with heart speckle tracking ultrasound US (SAFE 2014, NCT2236806). We recently assessed the interobserver variability in heart substructures delineation in patients included in this trial and here we present the relationship between dose received by heart substructures and occurrence of subclinical heart damage. Material and Methods Heart substructures of 17 left sided patients treated within SAFE trial were delineated according to a pre-existing contouring guideline [4]. All patients underwent 3d conformal radiotherapy (3dCRT). Data about Dmean, Dmax, D98% and D2% were collected and reported for whole heart (WH), Left Atrium (LA), Right Atrium (RA), Right Ventricle (RV) and Left Ventricle (LV). Dose parameters were reported also for left ventricle segments: Anterior (Ant), Lateral (Lat), Apical (Api), Inferior (Inf) and Septal (Sep). Patients were assessed at 6, 12 and 24 months from enrollment with speckle tracking US. Variations in terms of 3D Left Ventricle Ejection Fraction (LVEF), End Diastolic Volume Index (EDVI), End Systolic Volume Index (ESVI) and Global linear Strain (GLS) between baseline and last available US were calculated. Receiver Operator Characteristic (ROC) curves were plotted to test the accuracy of different dose parameter to each heart substructure in predicting any subclinical damage. Results Overall, a significant variation in 3D LVEF, EDVI, ESVI and GLS was found in 12,9,9 and 8 patients, respectively. 3d LVEF was significantly affected by LV D98%, Lat Dmean, Lat Dmax, Lat D2%, Inf Dmean, Inf D98%. A significant impact on EDVI and ESVI was found for WH Dmean, WH Dmax, RV Dmean, RV D98%, RV D2%, RA Dmean, Lat Dmean, Inf Dmean, Sep D98%, Api D98%. GLS was affected only by LA Dmax. Dose significantly related to decrease in 3D LVEF, EDVI, ESVI and GLS are also reported (Table 1). No significant association was found between subclinical heart damage and other measured dose parameters.

level <0.05. Conclusion

Overall, our dosimetric data show significant cardiac protection. In our opinion, all left-sided breast cancer