ESTRO 2021 Abstract Book

S911

ESTRO 2021

Radiotherapy (RT) for breast cancer reduces the risk of local recurrence and the risk of breast cancer mortality. However, it could induce excess cardiovascular mortality and morbidity. The purpose of this study was to evaluate the benefit of voluntary deep inspiration breath-hold (DIBH) over a free-breathing (FB) technique to minimize cardiac substructures exposure in radiation therapy of left-sided breast cancer. Materials and Methods Thirty-three patients with left-sided breast cancer underwent DIBH and FB planning computed tomography scans. Cardiac substructures were contoured using the F. Duane's cardiac atlas. Treatment planning was generated for both CT scanners using 3D-conformal radiotherapy (50 Gy delivered in 25 fractions ± boost of 16 Gy). Dose-volume histograms were analysed for heart, left anterior descending coronary artery (LAD), left circumflex (LCx), left main coronary artery (LMCA), right coronary artery (RCA), left ventricule (LV) and left lung. Results Dose to heart, LAD, LCx, LMCA, RCA, LV, and left lung was significantly lower in DIBH plans than in FB. When DIBH was compared with FB, mean dose (Dmean) for heart was 3.08Gy [1.1- 4.2] versus 4.1Gy [ 1.2-5.9 ]; for LAD (Dmean/Dmax) 9.9Gy /21.5Gy versus 14.7Gy/ 33.6Gy (p<0.01); for LCx 1.1Gy/ 1.94Gy versus 1.25Gy/ 2.04 Gy (p=0.1); for LMCA 1.5Gy/ 1.88 Gy versus 1.78Gy/ 2.15 Gy (p<0.01); for RCA 1.2Gy /2.03Gy versus 1.33Gy /2.2 Gy (p<0.01) and for LV, 2.2Gy/ 23.6Gy versus 4.8Gy/ 35.2Gy ( p< 0.01), respectively. DIBH decreased Dmean for lung by 3.1Gy (8.9 Gy versus 12Gy). The V20Gy was 16.87% versus 18.38%. The V30Gy was 11.9 % versus 13.47%. Conclusion Deep-inspiration breath hold technique improves cardiac substructures dosimetry compared to FB. We support the preferential use of DIBH, especially, in patients with cardiovascular comorbidities. The mean cardiac dose is probably insufficient to assess the exposure of cardiac substructures. Therefore, we recommend to consider doses to LAD and LV in the planning optimization for left-sided breast radiotherapy PO-1094 Deep Breath Inspiration Hold Radiotherapy: innovative organ preservation technique. Our experience. S. Falivene 1 , V. Nardone 2 , M. Mormile 2 , P. Frallicciardi 2 , M. Cozzolino 2 , F.M. Giugliano 2 , C. Guida 2 1 Ospedale del Mare, ASL Napoli 1 centro, Radioterapia, Napoli, Italy; 2 Ospedale del Mare, ASL Napoli 1 centro,, Radioterapia, Napoli, Italy Purpose or Objective To match treatment planning in free breathing (FB) vs deep inspiration breath hold (DIBH) for patients with left side breast cancer valuating dosimetric difference to heart, left anterior descending artery (LAD). Respiratory cycle was also analysed to identify predictors of a better selection of patients that may benefit from this approach. Materials and Methods Thirty-eight patients with left breast carcinoma and candidate to radiotherapy were enrolled consecutively from 01/12/2018 to 31/12/2020. A CT scan in FB, the study of respiratory motion and then a DIBH TC were performed for all patients. During DIBH TC it was used SentinelTM to have a reference surface. Gating window was initially defined as 4 mm and then personalized on respiratory study. For visual feedback of the breathing position, the patients wore video glasses Epson Moverio BT200. During DIBH treatment it was used CatalystTM and portal imaging with iViewTM to evaluate target position. Tangential fields were used with field in field technique to optimize the dose distribution. Hypofractionated schedule of 20 fraction was used.Mean doses of both heart and LAD were evaluated. Respiratory cycle excursions was analyzed in order to identify a subpopulation of patients whit a greater benefit of DIBH technique. Both mean excursion FB (α ) and minimal excursion DIBH (β ) were used to obtain the ratio β/α. The median value of β/α was chosen as cutoff. Paired sample T-test was used to compare the differences of FB and DIBH technique in the two subgroups. Results All 38 patients were treated with DIBH with good compliance and no interruption. The mean heart dose was 2.69 Gy in FB vs 1.44 Gy in DIBH with an average reduction of 46%. The mean LAD dose was 10.13 Gy in FB vs 4.96 Gy in DIBH with an average reduction of 52%. Median β/α ratio was 4. Patients with a β/α <4 showed an average reduction of 27% for D mean heart and 34% for Dmean LAD (p-value>0,05 for both parameters), whereas patients with a β/α >4 showed an average reduction of 54% for Dmean Heart (p-value: 0,024) and 74% for DmeanLAD (p-value: 0,002). Conclusion DIBH is an excellent heart-saving technique, allowing adequate coverage of the target and without major obstacles in timing management in a modern radiotherapy department. Our analysis allow for an appropriate selection of patients that may benefit most from this technique. PO-1095 Reducing overall treatment time, a pilot RCT of neo-adjuvant radiotherapy in early breast cancer V. Vakaet 1 , H. Van Hulle 1 , G. Braems 1 , K. Vandecasteele 1 , W. De Neve 1 , H. Denys 2 , L. Veldeman 1 1 Ghent University, Human structure and repair, Ghent, Belgium; 2 Ghent University, Internal Medicine and Pediatrics, Ghent, Belgium Purpose or Objective Neo-adjuvant radiotherapy (NART) for breast cancer has shown improved disease free survival, and is common in other cancer types. However, there are some obstacles that complicate its introduction into daily practice. The fears are chemotherapy delay, an increase overall treatment time (OTT) and the risk of increasing surgical morbidity. Accelerated radiotherapy (RT) in 5 fractions allows to deliver NART in a very short time span and