Prognostic value of an integrated human papilloma virus and immunoscore model to predict survival in vulva squamous cell carcinoma

Abstract

Background: While the prognostic value of immune-related biomarkers is well characterized in many solid tumors, their significance in vulva squamous cell carcinoma (VSCC) remains unclear. Here, we report a comprehensive analysis of programmed death-ligand 1 (PD-L1) and immune cell infiltrates in VSCC and establish immunoscore models for classification of the disease. Methods: Archival tissues, immunohistochemistry, and digital quantification were used to investigate the number of CD4+, CD8+, CD68+, CD14+, FoxP3+, and PD-L1+ cells in epithelial and stromal compartments of VSCC (n=117). Immunoscores were developed by using these parameters and applying the least absolute shrinkage and selection operator (LASSO) to identify predictors of survival. Immunoscores were then integrated with HPV status, as determined by mRNA in situ hybridization, to construct internally validated nomograms. The models were assessed using Harrell's concordance-index (c-index), calibration plots, Kaplan-Meier curves, and decision curve analysis. Results: Advanced VSCC (FIGO stage III/IV) was characterized by high numbers of CD68+ macrophages and PD-L1+ cells (Spearmans correlation, ρ>0.80) in the epithelium. PD-L1 status independently predicted poor progression free survival (PFS) (HR=1.80, (95% CI (1.024-3.170), p=0.041). High stromal CD68+ or CD14+ myeloid cell infiltration was associated with poor PFS and disease specific survival (DSS) (p<0.05). Immunological parameters were used to determine immunoscores. Immunoscore^PFS and immunoscore^DSS were independent prognosticators of PFS (p=0.001) and DSS (p=0.007) respectively. Integrating immunoscores with HPV status (IS-HPV index) improved the prognostic impact of the models. The c-index of IS-HPV index^PFS was 0.750 for prediction of PFS compared to 0.666 for HPV status and 0.667 for immunoscore^PFS. The c-index of IS-HPV index^DSS was 0.752 for predicting DSS compared to 0.631 for HPV status and 0.715 for immunoscore^DSS. Conclusion: In summary, an index based on HPV status and an immunoscore built on PD-L1 expression and immune cell infiltrates could potentially serve as a prognostic tool to refine risk stratification in VSCC. Further validation is warranted to demonstrate clinical utility.