Heterogeneity of PD-L1 expression between invasive and lepidic components of lung adenocarcinomas

The dynamics of PD-L1 expression are poorly understood over the development of lung adenocarcinomas from pre-invasive lesions to fully invasive carcinomas. Given the importance of PD-L1 expression for the selection of patients to receive immunotherapy in the metastatic setting and possibly in the neoadjuvant setting, we sought to evaluate the agreement of PD-L1 expression in invasive and lepidic components of resected tumor specimens. We stained 86 adenocarcinomas for PD-L1 using the SP263 clone. We assessed the agreement of PD-L1 expression by tumor cells and immune cells between lepidic and invasive components. When both lepidic and invasive components were considered, PD-L1 positive immune cells and tumor cells were observed in 50 (58.1%) and 18 (20.9%) samples, respectively, using a ≥ 1% PD-L1 expression cutoff. Using a ≥ 1% cutoff for PD-L1 expression, positively stained tumor cells were observed in 11 (13%) lepidic and 15 (17%) invasive patterns, with agreement in 76 (88%) specimens and disagreement in 10 (12%) specimens (ĸ = 0.549). At ≥ 1% PD-L1 expression cutoff, PD-L1 positive immune cells were observed in 31 (35%) lepidic and 32 (37%) invasive patterns with an agreement of PD-L1 expression in 49 (57%) specimens and disagreement in 37 (43%) specimens (ĸ = 0.073). In our study of early stage adenocarcinomas of the lung, there was poor agreement in PD-L1 expression between paired invasive and lepidic components of tumors. Our data suggest that the non-invasive tumor components may not be as immunostimulatory as the invasive components, resulting in less adaptive expression of PD-L1.