ESTRO 2025 - Abstract Book

S3752

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2025

Purpose/Objective: To estimate the radiotherapy (RT) dose to circulating blood cells in patients with locally advanced non-small cell lung cancer (NSCLC), and to investigate its correlation with during- and post-RT white blood cells counts. Material/Methods: This study included 155 patients with locally advanced NSCLC treated with concurrent chemo-RT (cCRT) in 2004-2014. Patients received a median prescription dose of 63 Gy in 1.8-2 Gy fractions with 5-field intensity-modulated RT. An in house Artificial Intelligence (AI) auto-segmentation algorithm was developed to derive 19 blood-bearing structures (aorta, adrenals, compact bones, coronary arteries, esophagus, gallbladder, heart, inferior-vena-cava, kidneys, lung, liver, pulmonary arteries, pulmonary veins, pancreas, small intestine, superior-vena-cava, spleen, stomach, and spongy bones) from the planning CT scans. Dose-volume histograms (DVHs) of these structures were input into the Hematological Dose (HEDOS) computational framework to estimate dose to circulating blood cells (1,2). HEDOS simulates the whole-body blood flow and estimates the whole-body and per-organ blood dose (Figure 1). The percentage contribution of each organ to the total blood dose was calculated. Four blood DVH metrics (mean, standard deviation, 10th, and 90th percentile) were tested for association with pre-RT normalized lymphocytes, neutrophils, and the neutrophil-to-lymphocyte ratio at the during-cCRT nadir, and at 2 and 4 months post-cCRT. Applying linear regression modeling, the dataset was divided into a training and a set-aside validation set (70% and 30% split). A candidate DVH metric in training (defined by p<0.05) was tested for generalizability in the validation set.

Results: The population average estimated dose/fraction of circulating blood was 0.4±0.1 Gy. The corresponding 10th and 90th percentiles of the blood dose were: 0.27±0.08 Gy and 0.5±0.1 Gy. Among 19 organs, heart, lungs, aorta and superior-vena-cava were found to be the major contributing organs to blood dose (Figure 2). The during-cCRT neutrophil-to-lymphocyte ratio was significantly correlated with all four blood DVH metrics (coefficient of determination, R 2 =0.04-0.07; p=0.01-0.03) within the training set, and all blood DVH metrics generalized in the validation set (R 2 =0.08-0.09; p=0.04-0.05).