Spatial immunophenotyping of tumor-associated macrophages predicts prognostic outcomes in clear cell renal cell carcinoma

Abstract

Introduction Clear cell renal cell carcinoma (ccRCC), the most common kidney cancer subtype, has high rates of metastasis and recurrence. Its tumor microenvironment (TME), particularly tumor-associated macrophages (TAMs) and tumor-infiltrating lymphocytes (TILs), influences immune evasion and tumor progression. This study evaluated the prognostic significance of TAM and TIL subsets based on their phenotypes and spatial distribution within the TME. Materials and Methods This retrospective study included 643 ccRCC patients who underwent surgery at Asan Medical Center between 2011 and 2013. Multiplex immunofluorescence staining was performed on tissue microarrays from central and peripheral tumor regions. Markers for M1/M2 macrophages and T cells were quantified using automated imaging software, and optimal cutoffs were defined using maximally selected rank statistics, with additional sensitivity analyses performed to assess robustness. Survival outcomes were assessed with Cox regression, and group comparisons used appropriate statistical tests. Results High central density of M2-like TAMs (CD68+CD206+) was associated with poor overall, metastasis-free, and progression-free survival (PFS) (P < 0.05). In contrast, high central density of M1-like TAMs (CD68+iNOS+) was associated with favorable PFS (P = 0.034). M2-like TAMs were more abundant than M1-like across all tumor regions. Peripheral CD3+ TILs were more frequent than in the center. Exploratory analyses showed weak correlations between immune cell densities and response to tyrosine kinase inhibitor therapy. Conclusion Distinct phenotypes and spatial distributions of TAMs were associated with prognostic outcomes in ccRCC. Central M2-like TAMs were associated with poor outcomes, while central M1-like TAMs were linked to favorable prognosis. TILs did not demonstrate independent prognostic value.