Prognostic value of an integrated human papilloma virus and immunoscore model to predict survival in vulva squamous cell carcinoma
Authors: Elnour Rammah , Hindenes Ingjerd Helstrup , Færevaag Malene , Kolseth Ingrid Benedicte Moss , Thomsen Liv Cecilie Vestrheim , Johannessen Anne Christine , Costea Daniela Elena , Bjørge Line , Dongre Harsh Nitin 
Published: September 2024

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 using these parameters and applying the least absolute shrinkage and selection operator (LASSO) to identify predictors of survival. Immunoscores were integrated with HPV status, as determined by mRNAin situhybridization, 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. ImmunoscorePFSand immunoscoreDSSwere 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 indexPFSwas 0.750 for prediction of PFS compared to 0.666 for HPV status and 0.667 for immunoscorePFS. The c-index of IS-HPV indexDSSwas 0.752 for predicting DSS compared to 0.631 for HPV status and 0.715 for immunoscoreDSS.

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.

WHAT IS ALREADY KNOWN ON THIS TOPIC

Immunoscores have emerged as promising biomarkers in several solid tumors, however the prognostic potential of these models in vulva squamous cell carcinoma (VSCC) remains unexplored. Immunoscores are traditionally based on quantification of CD3+ and CD8+ T lymphocytes within the tumor core and invasive margin. However recent studies have highlighted the prognostic significance of additional immune cell subtypes, such as macrophages, in predicting patient survival. Advanced quantitative methods that enable the determination of immunoscores, incorporating expression of immune checkpoint proteins and infiltration of various immune cell populations within tumors, warrant further investigation.

WHAT THIS STUDY ADDS

This study investigates PD-L1 expression and distinct T lymphocyte and myeloid cell subsets within the spatial architecture of VSCC to identify immunological markers with prognostic value. Computational analysis identified PD-L1+ cells, CD8+ T lymphocytes, FoxP3+ T lymphocytes, and CD14+ myeloid cells as significant survival predictors in VSCC, leading to the development of immunoscores. These immunoscores demonstrated superior predictive performance compared to the individual parameters used to construct the models. Moreover, integrating immunoscores with HPV status and constructing, for the first time, an immunoscore-HPV index nomogram enhanced the prognostic accuracy and net benefit of the models.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

The immunoscore-HPV index proposed in this study holds potential as a rapid diagnostic tool to enhance risk stratification in VSCC and facilitate the identification of patients who may benefit from less aggressive treatment approaches. Incorporating immunoscores with clinicopathological or molecular features linked to carcinogenesis in prognostic models could improve classification strategies in VSCC and other cancer types.