Human leukocyte antigen expression in paired primary lung lesions and brain metastases in non-small cell lung cancer.

Abstract

43 Background: Human leukocyte antigens (HLA) are crucial for cytotoxic T cell responses to cancer. Loss of HLA expression is a mechanism of tumor immune escape and may contribute to resistance to immunotherapy. In patients with non-small cell lung cancer (NSCLC) treated with immune checkpoint inhibitors we have observed discordant responses between brain metastases and extracranial disease and reported on differential PD-L1 expression and clonal T cell infiltration between paired primary lung lesions and brain metastases. In this project we sought to evaluate whether HLA expression was retained in metastatic NSCLC. Methods: Adult patients with paired primary NSCLC and brain metastases were identified from our institution’s tissue registry. HLA-A cell membrane expression on tumor cells was determined by immunohistochemistry with an anti-HLA-A antibody. Tumors with greater than 10% HLA expression were considered positive. Agreement statistics (κ) and Fisher’s exact test were used for analysis. Results: 51 patients with paired primary NSCLC and brain lesions were identified. The median HLA expression was 20% in the primary tumors (IQR 0-65%) and 10% in the brain metastases (IQR 5-40%). 27 primary tumors and 24 brain metastases were positive for HLA expression. There was disagreement in HLA positivity between paired lesions in 11 patients (22%, 95% CI 12-35%)(κ = 0.57, 95% CI 0.35-0.79)(p = 0.0001). There was no significant difference in the time between the primary tumor and brain metastasis resections in patients with HLA expression disagreement compared to those with HLA expression agreement. None of the patients received immune checkpoint inhibitors for treatment of these lesions. Conclusions: We found significant differences in HLA-A expression on tumor cells in nearly one quarter of paired primary lung cancers and brain metastases. Differences in HLA expression may help explain the discrepancies in response to immune checkpoint inhibitors at different sites of disease and warrants further study.