Distribution of M1 and M2 macrophages and their impact on survival in non-small cell lung cancer

Tumor-associated macrophages play an essential role in carcinogenesis and metastasis. Our study aimed to evaluate the distribution of M1 and M2 macrophages in tumor islets and stroma and establish the impact on recurrence-free survival and overall survival in patients with surgically resected non-small cell lung cancer (NSCLC). 42 surgically treated NSCLC patients were recruited from the Sumy Regional Clinical Oncology Center. The inclusion criteria were age over 18, stages IA–IIIB of NSCLC, and absence of severe cardiovascular, pulmonary, or autoimmune diseases. Antibodies against CD68+ and CD163+ were used to determine the macrophage phenotype and their distribution in tumor islets and stroma. For each sample, six fields of view with a diameter of 1 mm were analyzed, focusing on the “hot spots” in the tumor stroma and islets. The average values method determined the cut-off value for macrophages M1 and M2. The cut-off values for total macrophages M1 was 28 cells/mm2, macrophages М1 in tumor islets – 18 cells/mm2, macrophages М1 in the stroma – 11 cells/mm2, total macrophages М2 – 38 cells/mm2, macrophages М2 in tumor islets – 13 cells/mm2, macrophages М2 in the stroma – 24 cells/mm2. All data about the clinicopathological characteristics of patients were collected from the medical records. The long-term follow-up period continued for at least 60 months. The difference between the studied groups was assessed using the Student's t-test and the Mann-Witney test. The Cox proportional hazards model was used to assess the impact of several clinicopathological characteristics on patient survival. Most M1 and M2 macrophages accumulated in the stroma (p<0.001). The total number of M1 macrophages was higher in men than women (p=0.0082). Pro-inflammatory macrophages were more prevalent in men than women in both the tumor islets (p=0.0192) and stroma (p=0.0226). Patients with the T1a–2a category had more total M1 macrophages than those with the T2b-4 category (p=0.0486). The tumor stroma also observed this trend (p=0.0205). Current and former smokers had a significantly higher number of M1 macrophages in tumor islets (p=0.0485). In squamous cell carcinomas, the total number of M2 macrophages was higher than in adenocarcinomas (p=0.0343), especially in the tumor stroma (p=0.0006). In conclusion, high M1 macrophage infiltration of tumor islets is associated with better recurrence-free survival. A low total number of M2 macrophages and their low expression in the stroma are associated with better overall survival in surgically treated NSCLC patients.