ESTRO 2025 - Abstract Book

S1427

Clinical - Lung

ESTRO 2025

Purpose/Objective: Since concurrent chemoradiotherapy (cCRT) followed by immunotherapy maintenance became the standard of care for unresectable LA-NSCLC, clinical outcomes have considerably increased. Based on the results of RTOG 0617, a reduction of cardiac dose might further improve survival and therefore dose to the heart and more recently to individual cardiac substructures (CS) has become a major concern. The aim of our study is to evaluate the correlation between RT dose CS and cardiac toxicity in a real-world cohort. Material/Methods: We retrospectively analyzed 45 pts consecutively treated with cCRT or exclusive RT between 2018 and 2022 affected by unresectable IIIA-IIIC NSCLC (TNM 8th edition). All pts received curative RT doses, in line with current ESMO guidelines (60-66 Gy/30-33 fraction) using VMAT or Tomotherapy. After anonymization of pts' treatment plan, CS were manually delineated by two junior radiation oncologists and revised by at least a senior physician, based on commonly used cardiac atlas (left anterior descending artery (LAD), sinoatrial node (SAN), atrioventricular node (AVN) and heart base). RT doses to CS were calculated and analyzed. Results: Forty-five pts with a median age of 71 years (45-85) were evaluated (28 males (62.2%) and 17 females (37.8%)). Median follow-up was 36 months. Five-year OS, MFS and PFS were 49.3%(SE±8.0%), 53.8%(SE±8.1%) and 31.3%(SE±8.3%), respectively. In four pts, adaptive replanning had to be performed due to anatomy modifications. Median whole heart (WH) mean doses in the full cohort was 7.98 Gy (0.06-22.5 Gy). Overall acute toxicity was low: only 6 pts experienced grade>=3 toxicities (4 hematological, 1 hemoptysis, 1 cardiac). In 8 pts cardiac conditions were observed after RT that were not reported before treatment (Table 1).

In these pts, median and mean WH mean dose were 6.55 Gy (0.06-14.11 Gy) and 6.7 Gy, while median and mean max dose to SAN, AVN and V10 to heart base were 23.75 Gy/23.84 Gy, 4.25 Gy/5.86 Gy and 67%/52%, respectively, thus not significantly different from the total cohort. Only one other late side effects >= grade 3 were observed (pneumonitis). Conclusion: In line with the secondary analysis of RTOG0617, heart exposure achieved with modern RT techniques (IMRT/VMAT) seems to result in low RT related cardiac toxicity when standard RT doses are used, even in pts treated with IT.