ESTRO 2020 Abstract book

S98 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

Conclusion Though the effect of LET is small compared to the dominating physical dose, an increase in probability of MR‐ IC was showed with increasing LET values. It is therefore important to combine LET with dose in predictive models for MR‐IC. PD-0179 Clinical results of partial- and whole breast irradiation in early stage breast cancer J. Haussmann 1 , B. Wilfried 1 , S. Corradini 2 , B. Tamaskovics 1 , E. Boelke 1 , F. Djiepmo‐Njanang 1 , K. Kammers 3 , C. Matuschek 1 1 University Hospital Düsseldorf, Radiation Oncology, Düsseldorf, Germany ; 2 Ludwig-Maximilians-University, Radiation Oncology, Munich, Germany ; 3 The Johns Hopkins University School of Medicine, Division of Biostatistics & Bioinformatics-Department of Oncology, Baltimore, USA Purpose or Objective Adjuvant radiotherapy after breast conserving surgery is the standard approach in early stage breast cancer. However, the extend of breast tissue that has to be targeted with radiation has not been determined yet. Traditionally, the whole breast was covered by two opposing tangential beams. Several randomized have tested partial breast irradiation (PBI) compared to whole breast irradiation (WBI) using different radiation techniques. We aimed to assess whether PBI is an appropriate option and which patient group and which techniques might be suitable. Material and Methods We performed a systematic literature review searching for randomized trials comparing WBI and PBI in early stage breast cancer with publication dates after 2010. The meta‐ analysis was performed using the published event rates and the effect‐sizes for in‐breast tumor recurrence (IBTR), overall survival (OS), cancer‐specific survival (CSS) and disease‐free survival (DFS) as investigated endpoints. We also aimed to compare the PBI techniques for IBTR and OS as well as adverse event rates including cosmetic outcomes and adverse events. Statistical analysis was performed using the Microsoft Excel add‐in MetaXL 5.3 utilizing the inverse variance heterogeneity model.

level <0.05. Conclusion

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