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preliminary lung 4DCT

Early ventilation changes predicted end-of-treatment lung function after radiotherapy

Early-treatment ventilation direction persisted to treatment completion in most photon- and proton-treated patients, with the prediction model explaining 89% of variation.

RadOncToday · ·1 min read

KEY POINTS

  • This retrospective analysis used data from 71 patients with locally advanced lung cancer enrolled in a completed randomized trial: 48 received photon IMRT and 23 received passive-scattering proton therapy. All patients received concurrent chemoradiotherapy to either 74 Gy in 37 fractions or 66 Gy in 33 fractions.
  • Stress-based finite-element ventilation maps were generated from four-dimensional CT at planning, during the first two treatment weeks, and during the final treatment week. Voxel-level changes were normalized for tidal-volume variation and registered longitudinally to the planning scan.
  • Among patients whose ventilation had increased early in treatment, 74% retained the same direction of change at treatment completion. Corresponding agreement was 79% for photon-treated and 75% for proton-treated patients.
  • Among patients with an early ventilation decrease, 83% remained in the decreased-ventilation group at treatment completion. Agreement was 86% with photons and 82% with protons.
  • In univariate analysis, end-of-treatment ventilation was associated only with planning ventilation, early-treatment ventilation, and lung volume. Other evaluated clinical and treatment characteristics did not provide significant additional predictive information.
  • A linear regression model incorporating planning ventilation, early-treatment ventilation, and lung volume achieved an R² of 0.89, indicating strong internal agreement between predicted and observed end-of-treatment ventilation.
  • The study did not establish whether the observed ventilation changes predicted radiation pneumonitis, pulmonary-function decline, symptoms, or quality of life. Its retrospective single-institution design and dependence on repeated high-quality four-dimensional CT also limit immediate clinical implementation.

CLINICAL TAKEAWAY

Early four-dimensional CT ventilation may identify how regional lung function will evolve before radiotherapy is completed, potentially informing adaptive functional-lung avoidance. The model remains investigational until validated prospectively and connected to clinically meaningful toxicity and patient-reported outcomes.

SOURCE

International Journal of Radiation Oncology, Biology, Physics