921P - Divergent fates: The ambiguous role of M2-like TAMs in oropharyngeal cancer

Background

Incidence of oropharyngeal squamous cell carcinoma (OPSCC) increases due to rise in human papilloma virus (HPV) related cancers. The tumor microenvironment (TME) of HPV+ OPSCC is characterized as more immune tolerant, with higher density of tumor-infiltrating lymphocytes (TILs). The role of tumor-associated macrophages (TAMs) remains unclear. M2-like TAMs are correlated with impaired overall survival (OS) in other tumor types. This study characterizes the prognostic impact of M2-like TAMs in OPSCC.

Methods

Fifty-eight patients with primary OPSCC, undergoing definite treatment (surgery, radiotherapy, chemoradiotherapy or a combination), were included. FFPE samples were stained for P16, TILs (CD3, CD8, FOXP3) and TAMs (CD68, CD163 and CD206) markers. Semi-quantitative assessment of each marker, in the tumor nest(t) and stroma(s), was executed by a board certified pathologist. Survival estimates were calculated via the Kaplan-Meier method using the log-rank test, using the ad hoc calculated cut-off point. Uni- and multivariate analysis were performed via cox proportional hazard model.

Results

The median density of sCD3, sCD8, tCD68 and sCD206 TAMs was higher in P16+, compared to P16–, whereas FOXP3 and CD163 infiltration was similar according to P16 status. In univariate analysis, tumors with high leukocyte infiltrates (sTIL, sCD8, tCD8, sFOXP3, tCD68, sCD206) had a better overall survival (OS), whereas sTIL-high and tCD8-high were the only factors associated with DFS. High tCD68 (HR 0.19) and sCD206 (HR 0.40) were associated with improved OS in P16+ OPSCC, but not in P16-. sCD163 and tCD163 infiltration was not related to adverse outcomes in P16+ nor in P16-. Table: 921P

Clinical and immunohistochemical characteristics