Impact of prophylactic cranial irradiation on survival in extensive-stage small cell lung cancer receiving first-line chemoimmunotherapy: a propensity score-matched study.

BACKGROUND

Chemoimmunotherapy has emerged as the standard first-line treatment for extensive-stage small cell lung cancer (ES-SCLC), improving survival outcomes. However, the role of prophylactic cranial irradiation (PCI) in the context of chemoimmunotherapy remains undefined.

OBJECTIVES

This study aimed to evaluate the impact of PCI on overall survival (OS) in patients with ES-SCLC after chemoimmunotherapy administration.

DESIGN

Retrospective study.

METHODS

This retrospective analysis included 261 patients with ES-SCLC treated with first-line chemoimmunotherapy between January 2019 and December 2023. All patients underwent MRI scans to confirm the absence of brain metastases. After 1:2 propensity score matching (PSM), 46 and 81 patients were assigned to the PCI and observation groups, respectively. The primary endpoint was OS, with additional exploration of progression-free survival (PFS), the cumulative incidence of intracranial metastases, and intracranial progression-free survival (iPFS).

RESULTS

After PSM, the two groups were well-balanced in baseline characteristics. Survival analysis showed a median OS of 19.9 months (95% confidence interval (CI): 11.8-28.0) in the PCI group and 15.6 months (12.3-18.9) in the observation group, without a significant difference (hazard ratio (HR) = 0.763 (95% CI: 0.484-1.206), log-rank  = 0.265). PCI significantly reduced the risk of brain metastasis (Fine-Gray  = 0.002), with 1-year cumulative incidence rates of 13.8% (3.4%-24.2%) in the PCI group and 53.4% (41.3%-65.6%) in the observation group. Subgroup analysis showed that for ES-SCLC patients achieving a partial response to initial chemoimmunotherapy, the PCI group had longer median OS (25.7 months (95% CI: 15.4-36.1) vs 19.4 months (15.4-23.4); HR = 0.502 (0.284-0.886); log-rank  = 0.021).

CONCLUSION

PCI did not improve OS in ES-SCLC patients receiving first-line chemoimmunotherapy, while it may confer a survival benefit for patients who achieve remission following chemoimmunotherapy. In addition, PCI significantly reduced the incidence of brain metastases. These findings warrant further randomized studies for verification.