Objective:

To investigate the association of CD68+CD163+ M2-like tumor-associated macrophages (TAMs) with post-treatment resistance and survival outcomes in metastatic colorectal cancer (mCRC) patients receiving chemotherapy and bevacizumab.

Approach:

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Key Findings:

• Resistant patients had significantly higher proportions and densities of CD68+CD163+ M2-like TAMs and CD68+CD163+PD-L1+ M2-like TAMs compared to non-resistant patients (p < 0.05).
• Infiltration levels of these macrophage subsets were significantly associated with post-treatment resistance (p < 0.05).
• High density of intratumoral CD68+CD163+ M2-like TAMs was significantly associated with shorter overall survival (OS) (p < 0.05) and showed a trend toward shorter progression-free survival (PFS) (p = 0.06).
• Multivariate Cox regression indicated that dense intratumoral infiltration of CD68+CD163+ M2-like TAMs was independently associated with unfavorable OS and PFS.

Interpretation:

Limitations:

• The study is retrospective and involves a limited sample size of 44 patients.
• Further validation in larger cohorts is necessary to confirm the findings.

Conclusion:

Increased infiltration of intratumoral CD68+CD163+ M2-like TAMs is associated with poor prognostic outcomes for both PFS and OS in mCRC patients undergoing chemotherapy and bevacizumab treatment.