Potential synergistic effects of cranial radiotherapy and atezolizumab in non-small cell lung cancer: an analysis of individual patient data from seven prospective trials.

Background: The impact of cranial radiotherapy (RT) on overall survival (OS) of patients with brain metastasis (BM) from non-small cell lung cancer (NSCLC) receiving programmed death 1/programmed death-ligand 1 (PD-1/PD-L1) inhibitors remains unclear. We aimed to examine the effect of previous cranial RT on the efficacy and neurological toxicity of PD-1/PD-L1 inhibitors in the treatment of patients with NSCLC.

Methods: Patient-level data from seven prospective trials involving atezolizumab for the treatment of NSCLC [BIRCH (NCT02031458), FIR (NCT01846416), IMpower130 (NCT02367781), IMpower131 (NCT02367794), IMpower150 (NCT02366143), OAK (NCT02008227), and POPLAR (NCT01903993)] were pooled. Patients with baseline BM were divided into two subgroups based on previous cranial RT before initiation of treatment: patients with previously irradiated BM (iBM) and patients with non-irradiated BMs (niBM).

Results: The per-protocol population consisted of 4,714 patients, including 3,176 in the atezolizumab group and 1,538 in the comparator chemotherapy group. In the atezolizumab group, OS was better in patients with BM (n=308) compared to patients without BM (n=2,868) [hazard ratio (HR): 0.83; 95% confidence interval (CI): 0.70-0.98; P=0.028]. Among patients with BM, patients with iBM (n=280) had a numerically longer OS (HR: 0.66; 95% CI: 0.41-1.07; P=0.090) than those with niBM (n=28). Intriguingly, OS was longer in patients with iBM than those without BM before (HR: 0.83; 95% CI: 0.70-0.99; P=0.043) and after (HR: 0.40; 95% CI: 0.32-0.49; P<0.0001) propensity score matching, while OS was similar between patients with niBM and those without BM. The survival advantage of patients with iBM over those without BM was not observed in the chemotherapy group. Atezolizumab-related serious neurological adverse events occurred in 16 (0.6%) patients without BM, none in those with niBM, and 2 (0.7%) patients with iBM.

Conclusions: These data suggest potential synergistic effects of cranial RT and anti-PD-(L)1 therapy in NSCLC patients, which warrants further validation.