Assessment of blood and tissue myeloid derived suppressor cells (MDSC), clinicopathologic factors, and treatment response in urothelial carcinoma (UC) patients (pts) undergoing surgery.

Abstract

362 Background: MDSC are heterogeneous immunosuppressive cells with potential predictive/prognostic role in cancer. The association between MDSC, clinicopathologic factors and pathologic response in pts with UC merits evaluation. Methods: Peripheral blood and/or tissue was collected from 120 pts. MDSC were measured in fresh unfractionated whole blood (WB), in peripheral blood mononuclear cells (PBMC) and fresh tumor tissue. MDSCs were identified by flow cytometry in WB and defined as LinloCD33+/HLADR- ((T)otal MDSC). MDSC subsets were defined as LinloCD33+/HLADR- and (G)ranulocytic (CD15+CD14-), (M)onocytic (CD15-CD14+), (I)mmature (CD15-CD14-, CD11b+ ). MDSC populations were presented as % of live nucleated blood cells and as absolute numbers from WB. Spearman correlations (r) and Wilcoxon rank sum test were used to assess correlations between MDSC populations, clinicopathologic factors and pT0N0%. Results: Of 120 pts, 82 were non-metastatic: 58 had only blood, 23 had blood & tissue, 1 had only tissue available for analysis. Of these 82 non-metastatic pts, 70 were men, median age 68; 81 pts had primary UC histology, 1 small cell cancer, 24 had mixed UC histology; 24 had prior intravesical therapy, 34 had neoadjuvant therapy (79% cisplatin-based, 21% unknown), 4 pts had post-op recurrence. At cystectomy: 15/82 pT0, 22/82 pT3/4; 37/82 CIS; 8/78 pN+. Significant associations were seen between MDSC blood levels and mixed histology, CIS, pN+, and lower pT0N0% (Table). Tumor M-MDSCs were associated with pN+ (p=0.05). There was significant correlation between tumor and WB % M-MDSC (r=0.55, p=0.007), and tumor and WB % G-MDSC (r=0.46, p=0.03). Conclusions: Blood MDSC levels correlate with several clinicopathologic factors and may predict pathological complete response (pT0N0). Assessment of association between MDSC levels, outcome and immunotherapy response is ongoing including in metastatic pts. [Table: see text]