3549 - Time of Day Radiotherapy and Radiation Pneumonitis in Lung Cancer with Interstitial Lung Disease
Presenter(s)
H. Lu, A. Jiang, Z. Yuan, J. Yuan, B. Tian, F. Wang, Y. Xu, and D. Chen; Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China
Purpose/Objective(s): Lung cancer patients with comorbid interstitial lung disease (ILD) are at high risk for radiation pneumonitis (RP). However, evidence is lacking regarding whether different time-of-day (ToD) RT schedules influence the incidence of RP in this high-risk population, as well as the potential association between ToD-related RP and prognosis. Therefore, this study investigated the association between RT timing and RP, and analyzed the relationships among RT timing, RP, and survival outcomes.
Materials/Methods: A retrospective cohort study was conducted on 424 lung cancer patients with baseline ILD who were subjected to thoracic RT at a single institution (2020–2024). Radiotherapy fractions were categorized based on the primary time of administration: morning (06:00–11:59), afternoon (12:00–17:59), or nighttime (18:00–05:59). The primary endpoint was radiation pneumonitis (RP, graded according to CTCAE v5.0). The associations between the daily treatment time period and RP, OS, and PFS were evaluated using Cox proportional hazards models, with pre-specified adjustments for clinical factors, systemic therapy, RT technique, fractionation regimen, and lung/heart dose-volume parameters.
Results: RP incidence differed by ToD: afternoon 58.3%, morning 44.1%, night 40.3% (P = 0.023). Afternoon RT remained associated with higher RP risk vs morning in multivariable models (HR 1.42, 95% CI 1.02–1.98; P = 0.036). Night RT showed no excess risk versus morning in univariable analysis, but was associated with higher RP risk after full adjustment (HR 1.62, 95% CI 1.02–2.58; P = 0.043). In subgroup analyses using Afternoon as reference, RP risk reductions with Morning and Night schedules were most evident in younger patients and in men; in NSCLC, Morning (HR 0.64, 95% CI 0.45–0.92) and Night (HR 0.46, 95% CI 0.26–0.81) were associated with lower RP risk than Afternoon. RT ToD was not independently associated with overall survival (OS) or progression-free survival (PFS), whereas RP itself was independently associated with worse survival.
Conclusion: In lung cancer patients with comorbid ILD, afternoon RT is associated with an increased risk of RP, but not significantly associated with OS or PFS. Prioritizing morning RT scheduling, combined with lung-sparing treatment planning, may help reduce the risk of RP and improve prognosis.