[Usefulness of Immunostaining Scoring for Predicting Response to Single-Agent Nivolumab in Patients with Metastatic Renal Cell Carcinoma].

ABSTRACT

Although several biomarkers have been identified to predict prognosis in renal cell carcinoma (RCC), there are no evidence-based biomarkers to predict the response to immune checkpoint inhibitors. In this study, we focused on lymphocytes and tumor cells in the tumor microenvironment and investigated whether immunostaining scoring could predict the best overall response. We evaluated 32 patients with metastatic RCC (mRCC) who were treated with nivolumab monotherapy between August 2016 and July 2020. We performed immunostaining for CD8 T cells, TIA-1, PD-L1, and HLA class 1 in RCC tissues and assigned a score with a maximum of 4 points each, which we defined as histological score. The best overall response of nivolumab was observed in 4 patients (12.5%) with complete response (CR), 10 patients (31.3%) with partial response (PR), 5 patients (15.6%) with stable disease (SD), and 13 patients (40.6%) with progressive disease (PD). There was no significant difference in patient background between the CR＋PR＋SD group (19 patients) and the PD group (13 patients), but CD8 T cells were significantly higher and TIA-1 positive cells tended to be higher in the CR＋PR＋SD group (CD8 T cell p＝0.03, TIA-1 p＝0.07, PD-L1 p＝0.67, HLA class 1 p＝1.00). In univariate analysis, histological score ≥3 tended to contribute to the best overall response of nivolumab (p＝0.05). There was no significant difference in overall survival or cancer-specific survival after nivolumab administration between the two groups of patients with histological score ≥3 and those with histological score ＜3. In conclusion, immunostaining scoring based on CD8 T cells may be able to predict the efficacy of single-agent nivolumab in patients with mRCC.