PD-L1-expression patterns in large-cell neuroendocrine carcinoma of the lung: potential implications for use of immunotherapy in these patients: the GFPC 03-2017 “EPNEC” study

Few data are available on programmed cell-death-protein-1–ligand-1 (PD-L1) expression on large-cell neuroendocrine carcinomas of the lung (LCNECs). We analyzed PD-L1 expression on tumor (TCs) and inflammatory cells (ICs) from LCNEC patients to assess relationships between this expression, clinical characteristics, and disease outcomes.

PD-L1 expression was determined by immunohistochemistry with monoclonal antibody 22C3 in consecutive LCNEC patients managed in 17 French centers between January 2014 and December 2016.

After centralized review, only 68 out of 105 (64%) patients had confirmed LCNEC diagnoses. Median overall survival (OS) (95% CI) was 11 (7–16) months for all patients, 7 (5–10), 21 (10–not reached) and not reached months for metastatic, stage III and localized forms (p = 0.0001). Respectively, 11% and 75% of the tumor samples were TC+ and IC+, and 66% had a TC–/IC+ profile. Comparing IC+ versus IC– metastatic LCNEC, the former had significantly longer progression-free survival [9 (4–13) versus 4 (1–8) months; p = 0.03], with a trend towards better median OS [12 (7–18) versus 9.5 (4–14) months; p = 0.21]. Compared to patients with TC– tumors, those with TC+ LCNECs tended to have non-significantly shorter median OS [4 (1–6.2) versus 11 (8–18) months, respectively]. Median OS was significantly shorter for patients with TC+/IC– metastatic LCNECs than those with TC–IC+ lesions (2 versus 8 months, respectively; p = 0.04).

TC–/IC+ was the most frequent PD-L1–expression profile for LCNECs, a pattern quite specific compared with non-small-cell lung cancer and small-cell lung cancer. IC PD-L1 expression seems to have a prognostic role.