ESTRO 2020 Abstract book

S1100 ESTRO 2020

center. All patients were treated using a full or hybrid IMRT/VMAT technique, and 115 (89%) received a dose of ≥60Gy. The median PTV was 578 cm3, with a range of 48- 2053 cm3. The Mean lungdose (Gy), mean total lung-PTV V20, V10, V5 and contralateral lung V5 (in %) were 13 (12- 22), 22.3 (5.5-37.2), 30.9 (11.2-52.9), 41.9 (9.2-78.3) and 22.7 (0-69.9), respectively. The mean heart dose (Gy), mean heart V40 and V25 (%) were 14 (0.5-44), 14.4 (0- 60.4), 19.3 (0-65.6). Mean esophagus V65, V60 and V40 (%) were 5.6 (0-36), 21.6 (0-83) and 45.1 (0-94). Patients receiving sCRT or RT alone had a worse OS (HR: 2.8; 95%CI 1.6-4.9; p=0.001 and 3.1; 95%CI 1.6-6.1; p=0.001). The only significant predictor of overall survival was the size of the PTV in cm3 (HR PTV >700 cm3: 2.03; 95%CI 1.2-3.3; p=0.005). Doses to the heart and esophagus were not significant predictors for OS. Kaplan-Meier graphs of the OS (Figure 1) and OS related to mean heart doses (Figure 2) are shown below.

Cancer Center, Department of Medical Physics, Poznań, Poland Purpose or Objective Accurate CIED (Cardiac Implanted Electronic Devices) dose assessment is necessary during radiotherapy treatment to prevent the risk of CIED malfunction occurrence. The study aimed to measure the CIED doses and perform statistical analysis in terms of the correlation between measured dose relative to the irradiated area, irradiation technique and total dose of the PTV area. Material and Methods Dose measurements on CIED in 33 patients of the Greater Poland Cancer Center were performed during the first fraction using semiconductor detectors placed on the patient's skin, directly above the implanted pulse generator. The study analyzed dose measurements in all patients with CIED treated from October 2017 to March 2019, excluding patients irradiated in the pelvic area (Table 1). Descriptive and statistical analyses of data were carried out. Statistical analyses were performed using the IBM SPSS Statistics 25 program. The study used the chi-square (χ2) test for variable independence and the non- parametric Kruskal-Wallis (K-W) test for independent variables to compare data distributions. Contingency coefficients and correlation coefficients were calculated, and their significance for correlations. The level of significance in this chapter is alpha = 0.05. Results from the p <0.05 range were considered significant at the level of statistical tendency.

Conclusion Patients undergoing cCRT for stage III NSCLC had survivals similar to that reported in the literature. Using our IMRT/VMAT technique with a focus on contralateral lung sparing the PTV size correlated significantly with survival, but not the doses to the lungs, esophagus and heart. PO‐1878 Factors affecting the dose received by CIED during photon radiation therapy. W. Szyszka 1 , E. Konstanty 2 1 The Greater Poland Cancer Center, Departement of Radiotherapy II, Poznań, Poland ; 2 The Greater Poland

Results The mean dose received by the device during the whole radiotherapy process was 1.112 Gy with a standard deviation of 1.700 Gy. The Median was 0.52 Gy. The maximum dose received by CIED was 7.325 Gy. The level of correlation between the dose of CIED from the entire RT course and the total dose (PTV) is equal to 0.228 and the value of p = 0.202. The χ2 test statistics for independence between the CIED dose from the entire RT course and the irradiated area is