ESTRO 2022

Session Item

Breast

Session Code: 6006

Session Type: Poster (digital)

Track: Clinical

Factors affecting cardiac dose in left-sided whole breast radiotherapy in a single institution

Arpad Tot, Serbia

Presentation Number: PO-1216

Abstract

Abstract Title:

Factors affecting cardiac dose in left-sided whole breast radiotherapy in a single institution

Authors:

Arpad Tot^1,2, Borislava Petrović^1,3, Milana Marjanović^4,3, Ivan Gencel¹, Nemanja Golubovac¹, Olivera Ivanov^5,6, Jelena Ličina^5,6, Milana Mitrić-Ašković⁵

¹Oncology Institute of Vojvodina, Medical Physics, Sremska Kamenica, Serbia; ²Institute od Nucelar Sciences Vinca, Physics, Vinca, Serbia; ³University of Novi Sad, Faculty of Sciences, Physics, Novi Sad, Serbia; ⁴Oncology Institute of Vojvodina , Medical Phyiscs, Sremska Kamenica, Serbia; ⁵Oncology Institute of Vojvodina, Radiotherapy, Sremska Kamenica, Serbia; ⁶University of Novi Sad, Faculty of Medicine, Novi Sad, Serbia

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Purpose or Objective

Left-sided whole breast radiotherapy (RT) can increase the risk of cardiac disease with increasing dose. Therefore, one of the main concerns is to reduce excessive dose to heart, LAD and lungs. The purpose of this study was to assess the correlations of left lung volume, mean heart distance, chest wall separation with heart and lung dose in women with left-sided breast cancer receiving whole breast radiotherapy. The correlations are used during the CT scanning for immediate decision on the use of most appropriate technique for particular patient (breath hold techniques vs. free breathing).

Material and Methods

133 female patients treated with left-sided breast RT at Oncology Institute of Vojvodina (Sremska Kamenica, Serbia) between 2017 and 2020 were analyzed. Left lung volume (LLV), left lung mean dose (LLD), mean heart dose (MHD), heart dose V25 Gy, V20 Gy, V16 Gy, V8 Gy, left anterior descending artery (LAD) mean dose (LADm), LAD max dose (LADM), chest wall separation (CWS), central lung distance (CLD), max heart distance (mHD) were collected from treatment planning system Monaco (Elekta, UK). A two-tailed Student's t-test and Pearson's correlation test were performed for statistical analysis.

Results

Median values were: left lung volume (LLV) was 1429.82 (462.80) cm³, chest wall separation (CWS) 22.77 (3.50) cm, max heart distance (mHD) 1.97 (0.60) cm, central lung distance (CLD) 0.96 (0.86) cm, mean heart dose (MHD) 2.28 (1.28) Gy, LAD mean dose (LADm) 30.27 (11.61) Gy, LAD max dose (LADM) 11.64 (6.99) Gy, mean left lung dose (LLD) 4.45 (1.45) Gy. Statistically significant (p< 0.05) negative correlations was found between LLV and MHD (r=-0.546), HD V25 (r=0.-500), HD V20 (r=-0.536), HD V16 (r=-0.563), HD V8 (r=-0.618), LAD mean (r=-0.588), LAD max (r=-0.556). Positive correlation was wound between CWS and HDmean (r=0.342) and LLV and mean LLD (r=0.182). There was no statistically significant correlation between CWS and mean LLD, and CLD and MHD. For patients (N= 111) whose MHD < 3.2 Gy (clinically acceptable) mean CSW was 22.31 (3.49) cm and for patients (N=22) with MHD> 3.2 Gy mean CWS was 25.05 (2.61) cm.

Conclusion

RT improves survival rate, but also increases risk of heart diseases. A linear relationship between LLV and heart dose was observed. According to our results it is possible using (CWS vs. MHD) values to determine if there is a need for breath hold technique already on CT without making RT plan. In our Institute acceptable MHD is 3.2 Gy, which is in most cases accomplished when CWS is bellow 25 cm. Beside the observed (CWS) criteria, MHD should be considered during planning when determining the most appropriate RT technique. This reduces the time between CT simulation and beginning of the RT treatment and travel costs for patients. CWS correlation could be promising clinical parameter since it could offer an estimation of mean heart dose and necessity of deep inspiration technique.