Clinical Efficacy of Atezolizumab in PD-L1 NSCLC Subgroups
Patients with programmed cell death ligand 1 (PD-L1)–negative non–small cell lung cancer (NSCLC) treated with atezolizumab may experience an overall survival benefit regardless of the PD-L1 immunohistochemistry (IHC) assay used. This was the finding of research presented by Shirish Gadgeel, MD, of Barbara Ann Karmanos Cancer Institute, Detroit, at the 2017 European Society for Medical Oncology (ESMO) Congress (Abstract 1296O).
The previously reported phase III OAK trial demonstrated that atezolizumab resulted in improved median overall survival versus docetaxel in patients with advanced NSCLC, regardless of their PD-L1 status. To determine whether these results were consistent across PD-L1 assays, the investigators assessed the efficacy of atezolizumab in PD-L1 subgroups. Prospectively, they determined PD-L1 expression using the SP142 assay, and retrospectively, with the Dako 22C3 pharmDx PD-L1 assay.
Of the 850 patients in the primary population, 400 were evaluable by the 22C3 assay. Among patients with tumors found to be negative by SP142, 77% were also found to be negative by 22C3. An overall survival benefit with atezolizumab was observed in PD-L1–negative subgroups defined by either assay, and patients with the highest PD-L1 expression by either assay also experienced an improved clinical benefit.
“These data provide evidence of atezolizumab overall survival benefit in patients with PD-L1–negative tumors, irrespective of the PD-L1 IHC assay used,” the authors concluded.