ESTRO 2025 - Abstract Book

S1319

Clinical - Lung

ESTRO 2025

Material/Methods: One hundred and nineteen (119) patients with stage-III NSCLC receiving concurrent CRT were retrospectively analyzed. Serial resting heart rate (rHR) measurements were prospectively collected weekly over the RT course and during regular follow-up visits until 18 months post-RT completion. The change from the baseline levels of rHR (rHR), as well as the incidence, frequency, and timing of tachycardia—a hallmark of autonomic dysfunction (AD) defined as rHR>100 beats per minute (bpm)—were characterized longitudinally during and following RT. Results: On average, 50.6 rHR serial measurements were taken from each patient during the study period, 12.73 of which were taken during the 7-week RT course. Mean rHR elevation from baseline started immediately after RT initiation, reaching the significance level (α=0.05) at Week 4 and increasing through the end of RT (rHR Baseline =84 bpm ±12 standard deviation, SD vs. rHR W4 =89±12, rHR W7 =92±13 bpm, p<0.0001, Fig 1 ). The upward rHR trend persisted through the follow-up period, peaking at one month post-RT (93±13 bpm, p<0.0001) and de-escalating afterward, reaching back to the baseline level at 6 months post-RT (86±16 bpm, p=0.2). The percentage of patients experiencing at least one episode of de-novo tachycardia during their RT was 53% (n=57), out of whom 48% suffered from persistent tachycardia (>3 separate tachycardia episodes during RT). The tachycardia incidence monotonically increased as the treatment progressed, peaking at Week 7 ( Fig 2 -left). Both the frequency of tachycardia episodes per patient and the percentage of the cohort experiencing tachycardia significantly increased from baseline after RT initiation and lasted through 6 months of follow-up ( Fig 2- right). Conclusion: In patients with NSCLC treated with concurrent chemo-RT followed by consolidative IO, significant and persistent elevation of resting heart rate was observed during CRT and persisted over time, indicating potential interaction of cardiac RT exposure on the autonomic nervous system (ANS). Further research will study the underlying cause of the ANS disruption, including irradiation of pulmonary veins and the conduction system.

Keywords: Cardiac radiation, autonomic dysfunction

References: 1. Fox, K. et al. Resting Heart Rate in Cardiovascular Disease. J Am Coll Cardiol 50, 823–830 (2007). 2. Stachowiak, P. et al. Heart rate variability during and after chemotherapy with anthracycline in patients with breast cancer. Kardiol Pol 76, 914–916 (2018). 3. Lee, D. H. et al. Resting heart rate as a prognostic factor for mortality in patients with breast cancer. Breast Cancer Res Treat 159, 375–384 (2016).