Comparison of SP142 and 22C3 Immunohistochemistry PD-L1 Assays for Clinical Efficacy of Atezolizumab in Non-Small Cell Lung Cancer: Results From the Randomized OAK Trial

Clin Lung Cancer. 2022 Jan;23(1):21-33. doi: 10.1016/j.cllc.2021.05.007. Epub 2021 May 30.


Background: This phase III OAK trial (NCT02008227) subgroup analysis (data cutoff, January 9, 2019) evaluated the predictive value of 2 PD-L1 IHC tests (VENTANA SP142 and Dako 22C3) for benefit from atezolizumab versus docetaxel by programmed death ligand 1 (PD-L1) status in patients with previously treated metastatic non-small cell lung cancer.

Methods: PD-L1 expression was assessed prospectively with SP142 on tumor cells (TC) and tumor-infiltrating immune cells (IC) and retrospectively with 22C3 using a tumor proportion score (TPS) based on TC membrane staining. Efficacy was assessed in the 22C3 biomarker-evaluable population (22C3-BEP) (n = 577; 47.1% of SP142-intention-to-treat population) and non-22C3-BEP (n = 648) in PD-L1 subgroups (high, low, and negative) and according to selection by 1 or both assays.

Results: In the 22C3-BEP, overall survival benefits with atezolizumab versus docetaxel were observed across PD-L1 subgroups; benefits were greatest in SP142-defined PD-L1-high (TC3 or IC3: hazard ratio [HR], 0.39 [95% confidence interval (CI), 0.25-0.63]) and 22C3-defined PD-L1-high (TPS ≥ 50%: HR, 0.56 [95% CI, 0.38-0.82]) and low (TPS, 1% to < 50%: HR, 0.55 [95% CI, 0.37-0.82]) groups. Progression-free survival improved with increasing PD-L1 expression for both assays. SP142 and 22C3 assays identified overlapping and unique patient populations in PD-L1-high, positive, and negative subgroups. Overall survival and progression-free survival benefits favored atezolizumab over docetaxel in double PD-L1-positive and negative groups; patients with both SP142- and 22C3-positive tumors derived the greatest benefit.

Conclusions: Despite different scoring algorithms and differing sensitivity levels, the SP142 and 22C3 assays similarly predicted atezolizumab benefit at validated PD-L1 thresholds in patients with non-small cell lung cancer.

Keywords: Biomarker-evaluable population; Inter-assay concordance; Overall survival; Programmed death ligand 1; Progression-free survival.

Publication types

  • Pragmatic Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Monoclonal, Humanized / therapeutic use*
  • Antineoplastic Agents / therapeutic use
  • B7-H1 Antigen*
  • Carcinoma, Non-Small-Cell Lung / drug therapy*
  • Docetaxel / therapeutic use
  • Humans
  • Immune Checkpoint Inhibitors / therapeutic use*
  • Immunohistochemistry*
  • Lung Neoplasms / drug therapy*
  • Retrospective Studies
  • Treatment Outcome


  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents
  • B7-H1 Antigen
  • Immune Checkpoint Inhibitors
  • Docetaxel
  • atezolizumab

Associated data