ESTRO 2022 - Abstract Book

S1030

Abstract book

ESTRO 2022

1 Oncology Institute of Vojvodina, Medical Physics, Sremska Kamenica, Serbia; 2 Institute od Nucelar Sciences Vinca, Physics, Vinca, Serbia; 3 University of Novi Sad, Faculty of Sciences, Physics, Novi Sad, Serbia; 4 Oncology Institute of Vojvodina , Medical Phyiscs, Sremska Kamenica, Serbia; 5 Oncology Institute of Vojvodina, Radiotherapy, Sremska Kamenica, Serbia; 6 University of Novi Sad, Faculty of Medicine, Novi Sad, Serbia 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). Materials 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) cm 3 , 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. 1 Fortis Hospital , Department of Radiation Oncology, Mohali, India; 2 Fortis Hospital , Department of Radiation Oncology, Mohali , India; 3 University of Chicago , The College of Liberal Arts and Science , Chicago , USA Purpose or Objective Adjuvant regional nodal irradiation (RNI) inclusive of internal mammary nodal chain (IMC), remains contentious for locally advanced carcinoma breast. This retrospective study proposes to assess planning outcomes for IMC in left chest wall by Volumetric Arc Therapy (VMAT) with “intentional avoidance”. Adjuvant regional nodal irradiation (RNI) inclusive of internal mammary nodal chain (IMC), remains contentious for locally advanced carcinoma breast. This retrospective study proposes to assess planning outcomes for IMC in left chest wall by Volumetric Arc Therapy (VMAT) with “intentional avoidance”. Materials and Methods Ten patients with left sided locally advanced carcinoma breast (post chemotherapy and Modified Radical Mastectomy) were included. Monaco™ Treatment Planning System (TPS) was utilized to develop two sets of plans (twenty) with uniform planning specifications. All subjects had left sided Supraclavicular Fossa (SCF), Level III, IMC and Chest Wall segmentation peer reviewed for uniformity by two separate physicians. Plan evaluation using standard dose volume histogram (DVH) parameters had: 95% of prescribed doses to CTV, Conformity Index (CI), Homogeneity Index (HI), Integral dose (ID), Dmean, Dmax and dose volume received by critical structures such as heart, left lung, right lung, liver, spinal cord and contralateral breast. A 60% isodose coverage was clinically significant for “incidental” dose to IMC after generation of VMAT with IMC (W- IMC) [as reference] & without IMC (WO-IMC) plans. Results An average of 8.6 nodes were involved in histopathological assessment. Results were analyzed and recorded as W-IMC and WO-IMC respectively: Dose prescription for 95% CTV was 97.6±1.5%, vs. 98.2±1.6%; Dmean Heart 783.6±106.5cGy vs. 774.1±108.0cGy, V20 Left Lung 29.1±0.5% vs. 28.8±1.5% CI 1.11±0.1 vs. 1.10±0.01; HI 0.975±0.01 vs. 0.977±0.02. No significant dose difference were seen in liver, spinal cord, contralateral breast, and ID between W-IMC and WO-IMC plans (p>0.05). A considerable variation in average incidental dose to 60% of IMC was recognized; W-IMC (5176.8±63.4 cGy) vs. WO-IMC, (4257.1±38.6 cGy) (p<0.05). PO-1217 Impact of intentional avoidance of internal mammary nodes by VMAT in left chest wall irradiation N.K. BHALLA 1 , A. Puri 2 , M. P 2 , P. D 2 , M. M 2 , P. Bhalla 3

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