The role of prophylactic cranial irradiation (PCI) in treating extensive-stage small-cell lung cancer (ES-SCLC) has been controversial. This study aimed to comprehensively analyze the efficacy of PCI for the treatment of ES-SCLC under active brain magnetic resonance imaging (MRI) surveillance.

Patients with ES-SCLC with no brain metastases (BM) confirmed by MRI at the time of diagnosis who responded well to first-line chemoimmunotherapy at three general hospitals were retrospectively included. Overall survival (OS), progression-free survival (PFS), and cumulative incidence of BM were compared between patients who underwent PCI and those who did not.

In total, 66 consecutive patients treated between March 2019 and December 2021 were included in our dataset. Seventeen patients underwent PCI (PCI group) and 49 patients did not (non-PCI group). In comparison with the non-PCI group, PCI did not provide OS (median OS: 18.53 vs. 17.35 months, p = 0.28) or PFS (median PFS: 8.61 vs. 7.56 months, p = 0.41) benefits. When death was counted as a competing risk, the difference in the cumulative incidence rate of BM was not statistically significant (1-year: 12.79% vs. 38.09%; p = 0.14).

Compared to active MRI surveillance, first-line chemoimmunotherapy followed by PCI did not improve the prognosis of patients with ES-SCLC. Further studies are warranted to evaluate the therapeutic effects of PCI following chemoimmunotherapy.