Background: Although the prognosis of patients experiencing recurrences after surgery for pancreatic cancer is extremely poor, patients who develop recurrence in the lung have a better prognosis compared to other types of recurrence. We performed a histo-immunological analysis of the metastatic specimens to identify specific features of this patient subgroup.
Methods: We performed immunohistochemistry for CD4+, CD8+, CD45RO+, Foxp3, and PD-L1 in the lung (n = 22), peritoneal (n = 18), and liver (n = 6) metastases of pancreatic cancer. As microenvironmental and immunonutritional investigations, the tumor-stroma ratio and prognostic nutritional index (PNI) were utilized in the integrative analysis of immunological features.
Results: We identified significantly increased tumor-infiltrating CD4+, CD8+, and CD45RO+ cells in lung metastasis, compared with peritoneal and liver metastases (lung vs. peritoneum/liver, CD4: P < 0.001/P = 0.015, CD8: P < 0.001/P = 0.038, CD45RO: P = 0.022/P = 0.012). The CD8/Foxp3 ratio was higher in the lung than in the liver (P = 0.024). PD-L1 expression was significantly higher in lung metastasis than in peritoneal metastasis (P = 0.010). Furthermore, we found that lung metastasis had fewer cancer stroma than peritoneal metastasis (P < 0.001). A higher PNI was observed in patients with lung metastasis, and PNI was positively correlated with tumor-infiltrating lymphocytes in metastatic sites.
Conclusion: We identified that lung metastasis revealed an immunologically "hot" tumor with increased TILs and PD-L1 expression. This specific feature suggests that patients with lung metastasis can be candidates for immunotherapy, such as immune checkpoint inhibitors; therefore, our study provides a framework for developing individualized treatment strategies for this patient subgroup.
Keywords: Anti-tumor immunity; Cancer immunotherapy; Lung metastasis; Metastatic pancreatic cancer; Tumor-infiltrating lymphocytes.
© 2022. The Author(s) under exclusive licence to Japan Society of Clinical Oncology.