Purpose: We aimed to evaluate the effectiveness of prophylactic cranial irradiation (PCI) for "early brain metastasis", which occurs before extracranial recurrence (ECR), and "late brain metastasis", which occurs after ECR, in limited-stage small cell lung cancer (LS-SCLC).
Materials and methods: We retrospectively analyzed 271 LS-SCLC patients who underwent definitive chemoradiation. All patients were initially staged with brain magnetic resonance imaging and positron emission tomography. Intracranial recurrence (ICR), ECR, progression-free rate (PFR), and overall survival (OS) were analyzed as clinical endpoints. The competing risk of the first recurrence with ICR (ICRfirst) was evaluated. Significantly associated variables in multivariate analysis of ECR were considered as ECR risk factors. Patients were stratified according to the number of ECR risk factors.
Results: The application of PCI was associated with higher PFR (p=0.008) and OS (p=0.045). However, PCI was not associated with any of the clinical endpoints in multivariate analysis. The competing risk of ICRfirst was significantly decreased with the application of PCI (hazard ratio, 0.476; 95% confidence interval, 0.243 to 0.931; p=0.030). Stage III disease, sequential, and stable disease after thoracic radiation were selected as ECR risk factors. For patients without these risk factors, the application of PCI was significantly associated with increased OS (p=0.048) and a decreased risk of ICRfirst (p=0.026).
Conclusion: PCI may play a role in preventing early brain metastasis rather than late brain metastasis after ECR, suggesting that only patients with a low risk of ECR may currently benefit from PCI.
Keywords: Brain metastases; Competing risk regression; Prophylactic cranial irradiation; Small cell lung carcinoma.