ESTRO 2020 Abstract Book

S73 ESTRO 2020

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. SP-0155 Is heart dose matter more important in SBRT than 3DCRT? Y. Kirova 1 1 Institut Curie Ensemble Hospitalier, Department of Radiation Oncology, Paris cedex 05, France Abstract text Extracranial stereotactic external-beam radiation therapy (SBRT) has developed considerably in recent years and is now an important part of the therapeutic alternatives to be offered to patients with cancer. It offers opportunities that have progressively led physicians to reconsider the therapeutic strategy, for example in the case of local recurrence in irradiated territory or oligometastatic disease. The literature on the subject is rich but, yet, there is no real consensus on therapeutic indications as well as clear guidelines concerning the doses at organs at risk (OAR), especially in the cardiac substructures. This is largely due to the lack of prospective, randomized studies that have evaluated this technique with sufficient recoil. The heart doses are very important for patients treated for lung or mediastinal

tumours and the late complications of 3D conformal radiotherapy (3DCRT) are well known for patients presented with breast and thoracic tumours. However, RT- associated heart disease is often not manifested clinically until many years after RT, the clinical effectiveness of these approaches is less certain in patients treated by SBRT. The problem of the series with thoracic SBRT is that they are with small number of patients and short follow up period. Other important point is the high dose per fraction and this is not well known with the experience of 3DCRT. At the other hand, for patients with increased risk of cardiac complications, SBRT may present lower risks than surgery. The number of International Guidelines is limited but some examples are available for the everyday practice. For example, the RECORAD 2016 proposed in case of use of 3 fractions (of 15-18 Gy) schemes, to limit the maximal heart dose (Dose max) at < 30 Gy and D15ml<24Gy; in case of 5 fraction of 10Gy to respect the maximal dose (Dose max) at < 38 Gy and D15ml < 32Gy. The JROSG10-1 recommends D15cc < 40 Gy in case of 8-10 fractions. Larger prospective data, with longer follow up is needed to evaluate the tolerated dose and the irradiated volume with multidisciplinary discussion to establish solid guidelines and decrease the risk of long term toxicity. PH-0156 Pattern of care and outcomes in stage III esophageal cancer receiving definitive chemoradiation Y. Chou 1 , Y. Lee 1 , J. Chiou 2 , H. Chen 1 , H. Tseng 1 , C. Huang 3 , J. Huang 4 1 Chung Shan Medical University Hospital, Radiation Oncology, Taichung, Taiwan ; 2 Chung Shan Medical University, School of Health Policy and Management, Taichung, Taiwan ; 3 Chung Shan Medical University Hospital, Institute of Medicine, Taichung, Taiwan ; 4 Chung Shan Medical University Hospital, Department of Medical Research, Taichung, Taiwan Purpose or Objective Multimodality approach is recommended to treat stage III esophageal cancer (EsoC). However, the most optimal radiation dose to be delivered for patients receiving definitive chemoradiotherapy (dCCRT) is still in debate. Here we report the pattern of care and survival outcomes for stage III EsoC patients receiving dCCRT in Taiwan. Material and Methods Patients who were diagnosed as having stage III EsoC and received dCCRT between 2010 and 2015 were retracted from the Taiwan Cancer Registry database for analysis. The overall survival (OS) rates were calculated by the Kaplan-Meier method. The prognostic factors were identified by using the Cox regression hazards model. Results A total of 2047 patients were included in the study and the median radiation dose delivered is 5940cGy. Out of the entire cohort, 991 patients were allocated into the low- dose group (RT dose 4000-5939cGy) while 1056 patients were allocated into the high-dose group (RT dose ≥5940cGy). One-and 5-year OS were significantly better among patients in the high-dose group. Survival rates at 1 year were 52 % and 44% in the 2 groups, respectively. Survival rates at 5 years were 16% and 11% (p<0.0001) in the two groups, respectively. The prognostic factors for OS include radiation dose delivered, sex, cancer site, clinical T/N status, and body mass index. In subgroup analysis, those in the high-dose group showed a significant survival benefit in patients with cT3N1 (p= 0.0076), cT4N2 (p = 0.02) and cT4N3 (p = 0.0215) stage. Poster Highlights: Poster highlights 5 CL : GI