Detection of programmed cell death-ligand 1 using 22C3 antibody in patients with unresectable stage III non-small cell lung cancer receiving chemoradiotherapy.

BACKGROUND: The expression of programmed cell death-ligand 1 (PD-L1) is a biomarker for administering immune check point inhibitors in patients with advanced stage non-small cell lung cancer. Although the consolidation therapy of durvalumab after definitive chemoradiotherapy has become the new standard of care for patients with unresectable stage III non-small cell lung cancer, the prevalence and prognostic role of PD-L1 expression in this population remain unclear.
METHODS: We retrospectively reviewed data from patients with unresectable stage III non-small cell lung cancer who received definitive chemoradiotherapy at our institution between 2012 and 2017. Levels of PD-L1 were assessed using 22C3 antibody, and associations of progression-free and overall survival rates with PD-L1 statuses at a tumor proportion score cutoff of 1% were analyzed.
RESULTS: Among the 104 patients enrolled, PD-L1 statuses were as follows: tumor proportion score < 1%, 73 (70.2%); 1-49%, 21 (20.2%); and ≥ 50%, 10 (9.6%). The number of patients with stage III non-small cell lung cancer with pretreatment PD-L1 tumor proportion score ≥ 1% was less than the number with advanced stage disease. There was no association between patient characteristics and PD-L1 status, and no significant differences were observed in progression-free and overall survival rates relative to PD-L1 status.
CONCLUSION: Expression of PD-L1 in patients with stage III non-small cell cancer before chemoradiotherapy should be assessed because of the low prevalence of tumors with tumor proportion scores ≥ 1%. Further studies are needed to clarify whether durvalumab improves survival after definitive chemoradiotherapy, irrespective of tumor PD-L1 expression.