The impact of neoadjuvant therapy on the tumor microenvironment in rectal, esophageal, and pancreatic cancer – a cross-cancer analysis

Introduction: Neoadjuvant therapy (NeoTx) is a key approach in managing gastrointestinal cancers, aiming to reduce tumor size and enhance surgical outcomes. In addition to its direct impact on tumors, NeoTx plays a significant role in shaping the tumor microenvironment (TME), which is crucial for determining treatment outcomes. Alterations in lymphocytic, myeloid, as well as stromal cell profiles within the TME, can change immune responses, having impact on patients’ prognosis. This leads us to the hypothesis that NeoTx does not only have a direct impact through cytotoxicity but also operates indirectly through an immune cell-based manner. To address this, we employed a translational approach, bridging preclinical findings and clinical patient outcomes to gain a more holistic understanding of how NeoTx modulates the TME.

Methods: In our study, we investigated immune cell modulation in the TME using multiplex immunofluorescence that enabled simultaneous detection of six markers in formalin-fixed, paraffin-embedded (FFPE) tissue. For our investigation, we defined three panels: lymphocytic (CD3, CD4, CD8, CD20, FOXP3, PanCK), myeloid (CD11b, CD33, CD68, CD206, HLA-DR, PanCK), and stromal (CD11c, CD34, aSMA, NCAM, PRPH, PanCK). The cohort consisted of two groups: primary resected with a TNM-, sex-, and age-matched cohort of NeoTx-treated patients (N=234). For a more comprehensive understanding, we assessed pre-treatment biopsies of RCa- and EAC-patients (N=50) within the same cohort. Quantitative and spatial analysis was performed to assess shifts in immune cell populations and cell-cell interaction after NeoTx.

Results: NeoTx led to a significant increase in CD8+T cells and tumor-infiltrating lymphocytes, both associated with improved anti-tumor responses. A decrease in Tregs, known for their immunosuppressive functions, was also observed, reducing local immune suppression. In the myeloid compartment, NeoTx reduced the number of immunosuppressive M2-macrophages and myeloid-derived suppressor cells (MDSCs), while promoting a shift toward pro-inflammatory M1-macrophages.

Conclusion: NeoTx not only reduces tumor burden but also reshapes the immune cell profile, thereby enhancing anti-tumor activity. These findings underscore the value of a translational approach, to better predict treatment efficacy. This also supports the rationale for combining NeoTx with immunotherapies to improve outcomes in rectal and esophageal cancer.

Publication History

Article published online:
04 September 2025