ESTRO 2020 Abstract book

S917 ESTRO 2020

Results The use of ABC mDIBH resulted in similar target coverage with no significant statistical differences. Median LV-V5 was 34.6 cc (range: 13.0-67.2 cc) with FB and 11.5cc (range: 0.0-35.7 cc) with ABC (p<0.001), resulting in absolute and relative reduction of 19.9 cc (range: 1.8-43.8 cc) and 67.3% (range: 8.3-100%), respectively. The use of ABC mDIBH reduced LV-V5 by 35% or greater in 90% of patients. Using ABC mDIBH, the dosimetric reduction in LV-V5 translated in an average decrease of ACE 9-year excess cumulative risk from 0.7% to 0.3% for risk0 group, from 1.2% to 0.5% for risk0.8 group, from 1.7% to 0.8% for risk1.4 group and from 2.3% to 1.0% for risk1.8 group. The impact of ABC mDIBH on ACE cumulative risk becomes increasingly remarkable with patients’ age. F or patients age >60 years, ACE 9-year excess cumulative risk decreases from 1.6% to 0.9% for risk0 group, from 2.8% to 1.5% for risk0.8 group, from 4.1% to 2.2% for risk1.4 group and from 5.4% to 2.9% for risk1.8 group. Conclusion ABC mDIBH technique resulted in a significant reduction in left ventricular V5 for left-sided breast radiotherapy. Excess risk of ACEs can be remarkably reduced, in particular for patients age >60 years. PO-1594 Impact of mean heart dose on acute coronary event excess cumulative risk in breath-hold breast IMRT F. Deodato 1 , A. Ianiro 2 , M. Boccardi 1 , G. Macchia 1 , C. Romano 2 , P. Viola 2 , V. Picardi 1 , M. Ferro 1 , M. Ferro 1 , A. Pierro 3 , E. Scirocco 4 , M. Buwenge 4 , S. Cammelli 4 , C. Sacra 5 , C.M. De Filippo 6 , V. Valentini 7 , A.G. Morganti 4 , S. Cilla 2 1 Fondazione di Ricerca e Cura Giovanni Paolo II, Radiation Oncology Unit, Campobasso, Italy ; 2 Fondazione di Ricerca e Cura Giovanni Paolo II, Medical Physics Unit, Campobasso, Italy ; 3 Fondazione di Ricerca e Cura Giovanni Paolo II, Radiology Department, Campobasso, Italy ; 4 DIMES Università di Bologna, Radiation Oncology Department, Bologna, Italy ; 5 Fondazione di Ricerca e Cura Giovanni Paolo II, Cardiology and Hemodynamics Unit, Campobasso, Italy ; 6 Fondazione di Ricerca e Cura Giovanni Paolo II, Cardiovascular Surgery Department, Campobasso, Italy ; 7 Fondazione Policlinico Universitario A. Gemelli, Radiation Oncology Department, Roma, Italy Purpose or Objective Cardiac toxicity is a major concern for left breast tangential field irradiation. A relationship between mean heart dose (MHD) and acute coronary event (ACE) rate has been reported in literature, with a cumulative incidence of ACE increased by approximately 16% per Gy. Moderate deep inspiration breath hold (mDIBH) during radiation treatment delivery helps in reducing the cardiac dose. The aim of this study was to quantify how the use of active breath control (ABC) in mDIBH during tangential IMRT breast irradiation translated in a reduction of ACE excess cumulative risk. Material and Methods Twenty consecutive patients with left-sided breast cancer who underwent adjuvant tangential IMRT with ABC mDIBH were analyzed in this study. All patients underwent CT simulation in both free breathing (FB) and mDIBH. The Elekta ABC spirometer was used for respiratory control and breath-hold length of 20–30 s. A simultaneously integrated boost (SIB) plan was created for both simulation CTs (FB and mDIBH) consisting of a prescription dose of 50 Gy to whole breast and 60 Gy to the tumor bed in 25 fractions and tangential IMRT technique. ACE cumulative risk was calculated using the prediction model developed by van den Bogaard et al., depending on MHD, patient age and pretreatment risk factors (0 for no risk and 1 for diabetes or hypertension or history of

are shown in Table 1; they presented no significant difference (p <0.05), leading to a mean increase in the volume of the insert that remain constant along this range of phases.

Conclusion A phased 4D-CT dataset selected as reference CT images on the basis of constant volume could be used as reference for the target delineation and for registration with 4D- CBCT imaging in order to improve the treatment accuracy. PO-1593 Impact of left ventricular V5 on acute coronary event cumulative risk in breath-hold breast IMRT C. Romano 1 , A. Ianiro 1 , F. Deodato 2 , G. Macchia 2 , M. Boccardi 2 , V. Picardi 2 , M. Ferro 2 , M. Ferro 2 , M. Craus 1 , A. Pierro 3 , E. Scirocco 4 , M. Buwenge 4 , S. Cammelli 4 , C. Sacra 5 , C.M. De Filippo 6 , V. Valentini 7 , A.G. Morganti 4 , S. Cilla 1 1 Fondazione di Ricerca e Cura Giovanni Paolo II, Medical Physics Unit, Campobasso, Italy ; 2 Fondazione di Ricerca e Cura Giovanni Paolo II, Radiation Oncology Unit, Campobasso, Italy ; 3 Fondazione di Ricerca e Cura Giovanni Paolo II, Radiology Department, Campobasso, Italy ; 4 DIMES Università di Bologna, Radiation Oncology Department, Bologna, Italy ; 5 Fondazione di Ricerca e Cura Giovanni Paolo II, Cardiology and Hemodynamics Unit, Campobasso, Italy ; 6 Fondazione di Ricerca e Cura Giovanni Paolo II, Cardiovascular Surgery Department, Campobasso, Italy ; 7 Fondazione Policlinico Universitario “A. Gemelli, Radiation Oncology Department, Roma, Italy Purpose or Objective Cardiac toxicity is a major concern for left breast tangential field irradiation. Recent analyses reported a strong relationship between volume of the left ventricle receiving 5 Gy (LV-V5) and acute coronary event (ACE). Moderate deep inspiration breath hold (mDIBH) during radiation treatment delivery helps in reducing the cardiac dose. The aim of this study was to quantify how the use of active breath control (ABC) in mDIBH during tangential IMRT breast irradiation translated in a reduction of ACE Twenty consecutive patients with left-sided breast cancer who underwent adjuvant tangential IMRT with ABC mDIBH were analyzed in this study. All patients underwent simulation CT of both free breathing (FB) and mDIBH. The Elekta ABC spirometer was used for respiratory control and breath-hold length of 20–30 s. A simultaneously integrated boost (SIB) plan was created for both simulation CTs (FB and mDIBH) consisting of a prescription dose of 50 Gy to whole breast and 60 Gy to tumor bed in 25 fractions and tangential IMRT technique. ACE cumulative risk was calculated using the prediction model developed by van den Bogaard et al., depending on LV-V5, patient age and pretreatment risk factors. A weighted ACE risk score was used for the patient cohort (0 for no risk, 0.8 for diabetes, 1.4 for hypertension and 1.8 for history of ischemic cardiac events). ACE cumulative risk was calculated four times for each patient (once for each pretreatment risk factor) simulating four cohorts grouped on the basis of the four risk factors. excess cumulative risk. Material and Methods