ESTRO 2025 - Abstract Book

S1348

Clinical - Lung

ESTRO 2025

Purpose/Objective: The Dutch Lung Cancer Audit-Radiotherapy (DLCA-R) is a national registration which prospectively collects data on curative radiotherapy treatments in patients with lung cancer. We aimed to assess acute toxicity and overall survival (OS) in patients with limited-stage small cell lung cancer (LS-SCLC) who received concurrent thoracic chemoradiotherapy using either once-daily (OD) or twice-a-day (BID) irradiation. Material/Methods: Between January 2016 and December 2023, 1179 patients starting concurrent chemoradiotherapy for LS-SCLC were included in the DLCA-R. Concurrent treatment was defined as radiotherapy starting within 30 days of chemotherapy. PCI was administered according to institutional policy. For 384 patients, information about vital status was not available and these records were excluded from analysis. Acute toxicity was defined as non hematological severe toxicity grade 3-5 or radiation pneumonitis grade 2-5 within 3 months after irradiation. Overall survival (OS) was calculated from start of radiotherapy until day of death or last follow-up and the log-rank test was used to assess statistical significance. Acute toxicity, median and 5-year OS were compared in patients treated with OD versus BID thoracic radiotherapy. In a multivariable Cox proportional hazards model, differences in survival between the two treatment groups were evaluated, adjusted for age, sex, T stage, N stage and WHO performance score. For acute toxicity, a multivariable logistic regression model was constructed, controlling for the same parameters. Results: 795 patients with pathologically confirmed LS-SCLC were included in the analysis. 445 (56.0%) were female. Patients in the OD regimen more often had WHO performance score >2 (Table). 593 (74.6%) were treated BID and 202 (25.4%) were treated OD. Median OS in the entire cohort was 27.3 months (95% CI 25.4 – 31.1). Information about PCI was missing in 52.3%. In patients treated with BID irradiation, median OS was 29.7 months (95% CI 25.8 – 35.9) versus 24.7 months (95% CI 22.1 – 28.1) in the OD regimen (Figure; Log-rank p=0.059). The multivariable model showed no significant difference in OS in patients with the BID regimen (HR 0.83, 95% CI 0.67 – 1.03). Patients in the BID regimen had a higher frequency of acute toxicity (27.3% vs. 21.6%), which was not statistically significant in multivariable analysis (OR 1.38, 95% CI 0.93 – 2.08).