Durability of CNS disease control in NSCLC patients with brain metastases treated with immune checkpoint inhibitors plus cranial radiotherapy.

Background: Immune checkpoint inhibitors (ICIs) have excellent systemic activity and are standard first line treatment in EGFR/ALK wild type metastatic non-small cell lung cancer (NSCLC). However, their role in patients with brain metastases, which affects over 20% of patients and cause significant morbidity, is less clear.

Methods: We reviewed patients with EGFR/ALK wild-type mNSCLC with CNS metastases. Serial MRIs were reviewed to determine the time to intracranial progression (iPFS). Multivariate regression was performed to adjust for the disease-specific graded prognostic score (ds-GPA).

Results: We identified 36 ICI- and 33 chemotherapy-treated patients with baseline CNS metastases and available serial MRIs (average frequency:3.5 months). Baseline radiation was given except for 2 chemotherapy-treated patients with asymptomatic solitary metastasis. The CNS burden of disease was higher in the ICI-treated group (ICI:22% vs. chemotherapy:0% had >10 lesions; p = 0.02), but the utilization of WBRT was not (ICI:31% vs. chemotherapy:45%; p = 0.09). At the time of progression, CNS involvement was identified in 30 % of ICI-treated patients compared to 64 % of chemotherapy controls (p = 0.02). ICI-treated patients had superior iPFS (13.5 vs 8.4 months) that remained significant in multivariate analysis (HR 1.9; 95%CI 1.1--3.4). Superior CNS outcomes in ICI-treated patients were driven by the PD-L1 high subgroup where the 12-month cumulative incidence rate of CNS progression was 19% in ICI-treated PD-L1 ≥ 50%, 50% in ICI-treated PD-L1 < 50% and 58% in chemotherapy-treated patients (p = 0.03).

Conclusions: Remarkable CNS disease control is seen with baseline RT plus ICIs in patients with PD-L1 ≥ 50%. Strategies for delaying WBRT should be investigated in this subgroup of patients.