ESTRO 2020 Abstract book

S81 ESTRO 2020

into daily practice and substantially reduces the dose in the heart and the Left Anterior Descending coronary artery (LAD). However, it remains unclear whether this reduction of heart dose results in a lower risk of cardiovascular disease. Therefore, we conducted a prospective longitudinal study to determine whether the use of a breath-hold technique in left-sided breast cancer radiation therapy treatment is associated with less increase of the CAC scores. In this prospective longitudinal study, we compared Coronary Artery Calcium (CAC) scores determined before the start of whole breast irradiation with those determined approximately 7 years afterwards. Methods and materials Initially, we included 109 consecutive patients in this prospective study, all diagnosed with either DCIS or breast cancer. Changes in CAC scores were analysed in 87 breast cancer patients who were able to and agreed to undergo a follow-up CAC CT scan. Three groups were compared: 18 patients receiving right-sided radiotherapy (R-), 14 patients receiving left-sided radiotherapy without breath- hold (L-BH), and 55 patients receiving left-sided radiotherapy with breath-hold (L+BH). These patients were treated with the Active Breathing Control (ABC) breath-hold (BH) technique (Active Breathing CoordinatorTM, ABC, Elekta, UK). The compliance rate of this ABC technique is > 95%. Amongst other variables age and the use of statins were registered because statin use may affect CAC scores in the heart vessels by decreasing the fibro-fatty plaque component and increasing the calcified plaque component. We compared the CAC development over time of the L-BH and L+BH groups by an independent T-test of the change (Δ) in CAC scores between baseline and (median) 7.4 years of follow-up. Results When comparing the observed differences in CAC scores over time, a significant attenuation of increased CAC scores was found for L+BH, both for the overall CAC scores and for the Left Anterior Descending (LAD) coronary artery scores (p < 0.01 and p < 0.001, respectively). This effect of using the breath-hold technique was even more striking in the group with CAC scores >0 at baseline. The attenuated increase over time of the CAC scores in the L+BH group was robust to correction for age and statin use (overall: p = 0.03; LAD: p = 0.006). Discussion We compared the observed increase of CAC scores in our patients with the findings of a large prospective longitudinal cohort study in a healthy American and a healthy European Caucasian population. It appeared that the CAC scores increased with 20-25% per year in these 2 cohorts. In our cohort (patients CAC > 0 at baseline) we found a comparable increase for the three groups. The range we found was 17%-26% %, of which the L-BH group had the highest increase per year and the R group the lowest. Furthermore, it appeared that in the healthy population 20% of the subjects with CAC = 0 progressed to CAC > 0 within 4-5 years. After 7.4 years of follow-up, we found a mean progression of CAC in the group with CAC = 0 at baseline of 42%, 42% and 75% in the R, L+BH and L-BH groups, respectively. Conclusion After a median follow-up of 7.4 years, we found a significant attenuation of the increase in the CAC scores when using a breath-hold technique. This is a relevant finding since higher levels of CAC scores are associated with higher probabilities of coronary artery events and it underlines the importance of using BH in left sided whole breast irradiation. Finally, it appears that the increase in time of mean CAC scores in irradiated breast cancer patients are comparable with those of females not bearing breast cancer.

https://www.rcr.ac.uk/system/files/publication/field_p ublication_files/bfco2016_breast-consensus- guidelines.pdf (2) Dodwell, D, Taylor, C, McGale, P et al, 2019, Abstract GS4-02: Regional Lymph Node Irradiation in Early Stage Breast Cancer: An EBCTCG Meta-Analysis of 13,000 Women in 14 Trials, In: Proceedings of the 2018 San Antonio Breast Cancer Symposium: AACR; Cancer Res; 79(4 Suppl). 3) Thorsen, L.B, Offersen, B.V, Dano, H et al, 2016, DBCG-IMN: A Population-Based Cohort Study on the Effect of Internal Mammary Node Irradiation in Early Node- Positive Breast Cancer. J Clin Oncol; 34 (4): 314- 4) Poortmans, P.M, Collette, S, Kirkove, C et al for the EORTC Radiation Oncology and Breast Cancer Groups, 2015, Internal Mammary and Medial Supraclavicular Irradiation in Breast Cancer, N Engl J Med; 373: 317-27. 5) Whelan, T.J, Olivotto, I.A, Parulekar, W.R et al for the MA.20 Study Investigators, 2015, Regional Nodal Irradiation in Early- Stage Breast Cancer , N Engl J Med; 373: 307-16.

SP-0154 Effect of breath-hold in left-sided whole breast irradiation M. Mast 1 , J. Pekelharing 2 , M. Heijenbrok 2 , D. Klaveren Van 3 , L. Kempen Van - Harteveld 1 , A. Petoukhova 1 , A. Verbeek - De Kanter 1 , J. Schreur 4 , H. Struikmans 1 1 haaglanden Medical Centre, Radiation Therapy, Leidschendam, The Netherlands ; 2 haaglanden Medical Centre, Radiology, Leidschendam, The Netherlands ; 3 leiden University Medical Center, Medical Statistics, Leiden, The Netherlands ; 4 haaglanden Medical Centre, Cardiology, Leidschendam, The Netherlands Abstract text Several studies found that radiotherapy for left-sided breast cancer is associated with an increased risk of Coronary Artery Disease (CAD). It appeared that this increased risk is proportional to the mean dose to the heart. Therefore the heart dose should be as low as reasonably achievable when treating left-sided breast cancer patients with whole breast irradiation (WBI). Nowadays, better heart sparing is feasible making use of a breath-hold technique. This technique is easily applied