Addition of thoracic radiotherapy to a PD-L1 inhibitor plus chemotherapy regimen delays brain metastasis onset in extensive-stage small cell lung cancer patients without baseline brain metastasis.

Background: With the application of immune checkpoint inhibitors (ICIs) and the discovery of the synergistic effect of radiotherapy and immunotherapy, the intracranial benefit of thoracic radiotherapy (TRT) is receiving signiffcant clinical attention. The purpose of this study was to analyze the cranial benefits of ICIs and TRT in patients with extensive-stage small cell lung cancer (ES-SCLC) without baseline brain metastases (BMs).

Materials And Methods: From August 2019 to August 2022, data from patients diagnosed with ES-SCLC without baseline BMs were retroactively recorded. The Kaplan‒Meier method was used to calculate overall survival (OS), progression-free survival (PFS), and brain metastasis-free survival (BMFS), and the differences between the treatment groups were compared with the log-rank test. Risk factors associated with OS were analyzed via the Cox regression model.

Results: A total of 216 patients were included, with a median follow-up of 24.73 months. Among these patients, 137 (63.4%) received first-line ICIs combined with chemotherapy (ChT), including 32 patients treated with anti-programmed death 1 antibody (αPD-1) and 105 patients treated with anti-programmed death-ligand 1 antibody (αPD-L1), and 79 patients (36.6%) received first-line ChT alone. Compared with the ChT-alone group, the ICI + ChT group demonstrated significantly improved PFS (8.07 vs. 6.87 months; p < 0.001) and OS (19.83 vs. 13.80 months; p = 0.001). The addition of ICIs to the ChT regimen did not significantly delay the onset of BMs compared to that with ChT alone (16.93 vs. 12.67 months; p = 0.379). Notably, the addition of TRT to the αPD-L1 + ChT regimen significantly prolonged BMFS compared to that without TRT (20.27 vs. 8.80 months; p = 0.045).

Conclusion: In patients with ES-SCLC without baseline BMs, first-line chemoimmunotherapy significantly improves PFS and OS. However, it does not delay intracranial metastasis. The addition of TRT to αPD-L1 + ChT therapy significant delays the development of BMs.

Clinical Trial Number: Not applicable.