Shravan V. Gowrishankar, MD: No relevant relationships to disclose.
Introduction: Anti-EGFR therapy is approved for the treatment of locally or regionally advanced head and neck squamous cell carcinoma (HNSCC). Here, we investigate recruitment of pro-tumor and anti-tumor immune cells as a potential mechanism of action.
Methods: Tumor tissue from 2 patients with HNSCC who received the fluorescently labelled anti-EGFR agent panitumumab (pan800) as part of a clinical trial in 2024 were prepared in FFPE slides. The slides were stained for cytotoxic T cells (CD8+) and tumor associated macrophages (FAP+) and imaged. The distribution of CD8+ cells and FAP+ cells between 3 high drug areas (HDAs) and 3 low drug areas (LDAs) per slide were compared. T-tests were used to compare fluorescence between areas. Statistical significance was taken as p < 0.05.
Results: There was significantly greater CD8+ levels in HDAs (4799 FI) compared to LDAs (3254 FI) (p= 0.047). There was no significant difference in FAP+ macrophages between HDAs (961 FI) and LDAs (1197 FI) (p=0.3675).
Conclusions: There were greater levels of anti-tumor cytotoxic T cells in HDAs of tumor tissue compared to LDAs. This could highlight a potential mechanism of action of anti-EGFR therapy via recruitment of CD8+ T cells.
