207 - Real-World Results Comparing Treatment Outcomes: Once or Twice Daily Thoracic Radiotherapy in Younger and Older Patients with Limited-Stage Small Cell Lung Cancer

11:15am - 11:25am PT

Room 20/21

Presenter(s)

Floris Bosch, MD, PhD - Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital (NKI-AVL), Amsterdam, Noord-Holl

J. Belderbos¹, F. T. M. Bosch², and R. Damhuis³; ¹The Netherlands Cancer Institute (NKI-AVL), Amsterdam, Netherlands, ²Netherlands Cancer Institute, Amsterdam, Netherlands, ³Comprehensive Cancer Organization, Utrecht, Netherlands

Purpose/Objective(s):

The Dutch Lung Cancer Audit-Radiotherapy (DLCA-R) is a national registration that collects data on 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 and compare outcomes in two age groups.

Materials/Methods:

Data from the DLCA-R of LS-SCLC patients irradiated between 2016 and 2023 was analyzed. Acute 90-day toxicity and OS in patients treated with OD and BID thoracic radiotherapy were compared in patients younger and older than 70 years. In a multivariable Cox proportional hazards model, differences in survival between the 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 LS-SCLC patients starting concurrent chemoradiotherapy between 2016 and 2023 were included in this analysis. Mean age was 66.7 years (SD 8.7), 445 (56%) were female, and 738 (92.8%) had lymph node positive disease. 475 (59.7%) patients were younger than 70 years, of which 362 (76.2%) were treated with a BID regimen. In younger patients with a BID regimen, the median OS was significantly longer (BID: 37.5 months versus OD: 26.1 months, HR 0.67; 95% CI 0.50 – 0.88). In patients =70 years, 231 (72.1%) were treated with a BID regimen. There was no difference in OS between regimens (21.8 versus 24.3 months, HR 1.1; 95% CI 0.78 – 1.55). No difference in acute toxicity was observed for younger patients treated with BID (26.0%) versus OD (23.9%) (OR 1.17; 95% CI 0.71 – 1.99). Older patients with a BID regimen had numerically increased acute toxicity (28.1%) compared to older patients with a OD regimen (16.9%) (OR 1.72; 95% CI 0.91 – 3.43).

Conclusion:

We observed a significantly longer OS in younger LS-SCLC patients treated with a BID radiotherapy regimen, compared to younger patients with an OD regimen, without increase of acute 90-day toxicity. We did not observe a difference in OS between regimens in patients 70 years or older.