CD57 as a prognostic marker in Oral squamous cell carcinoma-A study within the NOROC project

Abstract

Background: Oral squamous cell carcinoma (OSCC) is a cancer arising from the epithelium lining the oral cavity. Despite improvement in both detection of disease and treatment protocols, the survival has not increased as expected. The survivors of OSCC also report a high grade of debilitating side-effects of the treatment. Prognosis and choice of treatment is mainly decided by the TNM-status. This classification does not consider the biological processes in the tumor microenvironment. It is thought that with the inclusion of a battery of histopathological markers, the prediction of prognosis and choice of treatment could further improve. This can cause both an increase in survival, as well as a decrease in unwanted side effects of treatment. In this thesis, CD57; an immunohistochemical marker of a subset of cytotoxic NK-cells is assessed as a possible prognostic marker for OSCC.

Method: This is a retrospective study of patients included in the Norwegian Oral Cancer Study (NOROC). A subset of 131 patients from the cohort were included. Inclusion criteria were tumor arising from the mobile part of the tongue, tumor tissue available for immunohistological staining and recipient of curative treatment. Tumor tissue samples were sent to the Pathology department at the University Hospital of Northern Norway in Tromsø for CD57 immunohistological staining. The slides were scanned and assessed digitally using the Olympus Olyiva data program. Assessing the marker was done using a hot-spot method, where areas of higher density of CD57 positive cells were scored. CD57 expression was divided in high and low expression groups. Kaplan-Meier analysis was performed to assess association between CD57 expression and disease specific 5-year survival.

Results: Patients with a higher density of CD57 positive cells had a higher 5-year survival rate than those with a low density, but the results were not statistically significant. While CD57 is defined as a specific marker for NK-cells, a subset of cells not compatible with NK-cell morphology, as well as background staining in some areas of tissue can have affected the CD57 scoring.

Conclusion: We could not validate CD57 as a reliable prognostic marker for OSCC. However, due to some unspecific immunohistochemical staining, the scoring method should be reassessed before a definite conclusion is drawn.