Evaluation of major histocompatibility complex class I expression in clear cell renal cell carcinoma as a prognostic tool.

Abstract

469 Background: After nephrectomy for clear cell renal cell carcinoma (ccRCC) approximately one-third of patients develop metastases. Yet, with currently used prognostic tools such as the TNM staging and the Fuhrman nuclear grade (FNG) system, it is difficult to accurately assess prognosis for each patient. Here, we evaluated Major Histocompatibility Complex Class I (MHCI) expression as a potential prognostic immune marker in ccRCC. Methods: Fifty-five post-nephrectomy patients that presented with localized ccRCC were included. All patients had four or more years of follow up. MHCI was stained in the tumor sections via immunohistochemistry. Then, via an automated image analysis algorithm MHCI expression was quantitated with the Positivity score, the ratio of positively stained pixels over the total number of pixels. Results: Mean MHCI positivity score of the cohort was 0.75 (SE= ±0.20). At the end of the follow-up period, the patients who were alive had higher MHCI expression (0.80 positivity score; SE ±0.14) than those who died of disease (0.62 positivity score; SE= ±0.16; t test, p<0.0001). MHCI positivity scores above the mean were associated with increased cancer specific survival (Mantel-Cox, p=0.0021). MHCI expression was higher among patients with no recurrence (0.80; SE= ±0.16) compared to those that recurred during the study period (0.70; SE= ±0.22; t test, p=0.017); and time-to-recurrence was longer in patients with above mean MHCI positivity scores (Mantel-Cox, p=0.017). Patients who were alive with recurrence had increased MHCI expression (0.81; SE= ±0.10) compared to those who succumbed to disease recurrence (0.62; SE= ±0.25; t-test, p=0.0009). No correlation was detected between FNG and tumor expression of MHCI (ANOVA, p=0.655, F=0.423) or between stage at presentation and MHCI tumor expression (ANOVA, p=0.734, F=0.311). Conclusions: With an automated high-throughput image analysis, this cohort shows that increased MHCI expression in ccRCC is associated with improved prognosis after curative nephrectomy.