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Purpose: 18 F-fluorothymidine (FLT) positron emission tomography (PET) enables sensitive imaging of bone marrow (BM) proliferation. Sequential FLT-PET/computed tomography scans before and during chemoradiation therapy (CRT) for non-small cell lung cancer were repurposed to investigate the dose-response effects of radiation on BM proliferation., Methods and Materials: Twenty-six non-small cell lung cancer patients underwent platinum-based CRT to 60 Gy in 30 fractions with FLT-PET/computed tomography scans at baseline, week 2 (20 Gy), and week 4 (40 Gy). FLT uptake in BM was isolated using Medical Image Merge software. Weeks 2 and 4 FLT-PET BM scans were fused with contemporaneous radiation isodose distributions. Relationships between radiation dose and FLT BM uptake (highest standardized uptake values within the volume and visual parameters) were analyzed using generalized linear and restricted cubic spline models. Percentage volumes of total BM without appreciable FLT uptake ("ablated") on weeks 2 and 4 FLT-PET scans were calculated by comparisons with baseline scans., Results: Thoracic FLT uptake was ablated in BM regions exposed to cumulative radiation doses ≥3 Gy by week 2. In all cases, BM FLT's highest standardized uptake values within the volume declined rapidly as the radiation dose increased. BM proliferation significantly decreased by >95% after ≥3 to 4 Gy at 2 weeks and ≥4 to 5 Gy at 4 weeks. The ablated BM volume increased from week 2 to week 4 as BM in the penumbra accumulated radiation dose. The median percentage of total BM ablated was 13.1% (range, 5.6%-20.3%) at 2 weeks and 15.7% (range, 9.2%-24.1%) at 4 weeks. Mean lymphocyte counts fell from a baseline of 2.01 × 10 9 /L to 0.77 at week 2 and 0.60 at week 4. Lymphocyte decline strongly correlated with the percentage of total BM ablated by week 4 (y = -46 to 1.64x; R 2 adj = 0.34; P = .001)., Conclusions: BM ablation associated with low-dose radiation exposure during CRT correlated significantly with lower week 4 lymphocyte counts. BM is a potential organ at risk, and reducing the BM volume exposed to ≥3 Gy may help preserve lymphocytes, which is essential for effective adjuvant immunotherapy., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Purpose: The aim of this study was to report pulmonary function tests (PFTs) and clinician-reported and patient-reported quality-of-life (QoL) outcomes on a cohort of patients with non-small cell lung cancer (NSCLC) treated with SABR., Methods and Materials: A total of 119 patients with NSCLC were treated with SABR in the prospective cohort SSBROC study of patients with T1-T2N0M0 NSCLC. PFTs and QoL measures were obtained at baseline pretreatment and at 6-month intervals. Here we report on the 6- to 18-month time points. Analysis of covariance (ANCOVA) methods adjusting for baseline analyzed potential predictors on outcomes of PFTs and patient-reported dyspnea at 18 months., Results: The only statistically significant decline in PFTs was seen in forced expiratory volume in 1 second (FEV 1 ) at 18 months post-SABR, with a decline of -0.11 L (P = .0087; 95% CI, -0.18 to -0.02). Of potential predictors of decline, only a 1-unit increase in smoking pack-years resulted in a -0.12 change in diffusing capacity for carbon monoxide (P = .026; 95% CI, -0.02 to -0.23) and a 0.003 decrease in FEV 1 (P = .026; 95% CI, -0.006 to -0.0004). For patient-reported outcomes, statistically significant worsening in both the European Organisation for Research and Treatment of Cancer Quality of Life Core Questionnaire (QLQ-C30 Version 3) and the lung module (QLQ-LC13) dyspnea scores occurred at the 18-month time point, but not earlier. No potential predictors of worsening dyspnea were statistically significant. There was no statistically significant decline in clinician-reported outcomes or global QoL scores., Conclusions: We found a statistically significant decline in FEV 1 at 18 months posttreatment. Smoking pack-years was a predictor for decline in diffusing capacity for carbon monoxide and FEV 1 at 18 months. Worsening of patient-reported dyspnea scores was observed, consistent with the expected progression of lung comorbid disease., (Crown Copyright © 2023. Published by Elsevier Inc. All rights reserved.)