ESTRO 2021 Abstract Book

S975

ESTRO 2021

In the study, 24 pts had ≤ 3 points in CCI (48%) and 26 pts had > 3 points (52%). Mean CCS in pts with CCI ≤ 3 points was 18.5 months and in pts with CCI > 3 points was 13 months. 15-months CSS was 83.3% in pts with CCI ≤ 3 points and 40.9% in pts with CCI > 3 points without statistically significant differences (p 0.755). Mean OS in pts with CCI ≤ 3 points was 16.8 months and in pts with CCI > 3 points was 11.5 months.15-months OS was 74.3% in pts with CCI ≤ 3 points and 32% in pts with CCI > 3 points (p 0.620). Toxicity in both groups was similar without differences between pts with CCI ≤ 3 points and CCI > 3 points. Only one grade 3 oesophagitis was registered in CCI ≤ 3 points group. Conclusion The Charlson comorbidity index is a system that evaluates 10 years life expectancy. According to our results and despite the short follow-up, pts with CCI ≤ 3 points have better OS and CSS than pts with CCI > 3 points. In both groups, hypofractionated radiotherapy was well-tolerated regardless the CCI. Although more studies are needed, CCI can be an important factor to evaluate in patients with lung cancer because it identifies pts with a high probability of mortality. For this reason, this score can be an useful tool to assess the most suitable treatment option, especially in patients with several comorbidities. PO-1176 Duration of acute esophageal toxicity in RT-CHT for NSCLC with different fractionation schedules J. Socha 1 , E. Wasilewska-Teśluk 2,3 , R. Stando 4 , Ł. Kuncman 5 , L. Kępka 1 1 Military Institute of Medicine, Department of Radiotherapy, Warsaw, Poland; 2 Ministry of the Interior and Warmian & Mazurian Oncology Centre, Independent Public Health Care Facility , Olsztyn, Poland; 3 Faculty of Medicine, University of Warmia & Mazury, Department of Oncology, Olsztyn, Poland; 4 Holy Cross Cancer Center, Department of Radiotherapy, Kielce, Poland; 5 Medical University od Lodz, Department of Radiotherapy, Lodz, Poland Purpose or Objective In our previously published prospective trial on accelerated hypofractionated radiotherapy with concomitant full dose chemotherapy (AHRT-CHT) for locally advanced non-small cell lung cancer (NSCLC) the rate of grade 3 and higher acute esophageal toxicity was similar to that reported for conventionally fractionated platinum- based concomitant radiochemotherapy (CFRT-CHT), but its duration was prolonged, exceeding two weeks in all but one patients. The aim of the current study was to compare the duration of G≥3 acute esophagitis (AE) between AHRT-CHT and CFRT-CHT. Materials and Methods Clinical data were retrospectively analyzed for 76 NSCLC patients treated with CFRT-CHT (60-66 Gy/2 Gy/30- 33 fractions) in five institutions during 2015–2020 and compared with the data of 92 patients treated with AHRT-CHT (58.8 Gy/2.8 Gy/21 fractions) in a prospective study. Maximum grade of AE, incidence, and duration of G≥3 AE were the endpoints of this study. Univariate and multivariate analysis were applied to correlate clinical and tumor characteristics, radiotherapy dose-volume parameters and chemotherapy compliance to these endpoints. Results The two groups were well-balanced with respect to the patient and tumour characteristics, apart from age and performance status – patients treated with AHRT-CHT were younger than with CFRT-CHT (median 63 vs. 65 years, p=0.02) and had better performance status (p=0.004). A total of 134 patients developed AE: G1, 62 patients (28 [36.8%] CFRT-CHT, 34 [37%] AHRT-CHT); G2, 48 patients (24 [31.6%] CFRT-CHT, 24 [26.1%] AHRT-CHT); G3 and higher, 24 patients including one G5 in AHRT- CHT group (11 [14.5%] CFRT-CHT, 13 [14.1%] AHRT-CHT), p=0.47. Completion of all planned cycles of chemotherapy (p=0.002) and higher mean biologically effective esophageal dose (p=0.04) were significant predictors for higher maximum grade of AE; older age was a predictor for higher incidence of G≥3 AE. The median duration of G≥3 AE in AHRT-CHT group was 30 days (interquartile range [IQR] 19.2–46.5) vs. 7 days (IQR: 4.2–10) in CFRT-CHT group, p=0.005. In multivariate analysis, AHRT-CHT schedule (p=0.008) and larger PTV volume (p=0.035) were significant predictors for longer duration of G≥3 AE. Conclusion For NSCLC patients treated with AHRT-CHT, the incidence of G≥3 AE is similar, but its duration is significantly prolonged compared to the patients treated with CFRT-CHT. Reporting only the rate of G≥3 AE in clinical trials may underestimate the real extent of the esophageal toxicity. We postulate that its duration should also be routinely reported to enable a proper comparison of the toxicity between different fractionation schedules in combined RT-CHT. PO-1177 A heart valves contouring atlas on average intensity projection 4D-CT for lung cancer radiotherapy J. Socha 1 , A. Rygielska 2 , B. Uziębło-Życzkowska 3 , J. Chałubińska-Fendler 1 , A. Jurek 3 , M. Maciorowska 3 , M. Mielniczuk 3 , P. Pawłowski 1 , D. Tyc-Szczepaniak 1 , L. Kępka 1 1 Military Institute of Medicine, Department of Radiotherapy, Warsaw, Poland; 2 Military Institute of Medicine, Department of Radiotherapy, Laboratory of Medical Physics, Warsaw, Poland; 3 Military Institute of Medicine, Department of Cardiology and Internal Diseases, Warsaw, Poland Purpose or Objective A detailed contouring atlas of the heart valves is lacking. Existing heart contouring atlases have not been evaluated on average intensity projection four-dimensional noncontrast computed tomography (AVE 4D-CT) scans, routinely used for organ-at-risk delineation in lung cancer radiotherapy (RT). As a first step of a planned prospective trial on imaging-based evaluation of RT-related cardiotoxicity in NSCLC, we aimed to develop the heart valves contouring atlas and to assess interobserver variation in delineation of the heart, its substructures, and coronary arteries on AVE 4D-CT scans, along with the impact of contour variation on