Correlation of myeloid-derived suppressor cells (MDSC) with pathologic complete response (pCR), recurrence free survival (RFS), and overall survival (OS) in patients with urothelial carcinoma (UC) undergoing cystectomy.

Abstract

437 Background: MDSCs play an important role in maintaining a tumor immunosuppressive microenvironment. The association of circulating levels of MDSCs with pCR (pT0N0) and outcomes was investigated in patients (pts) with non-metastatic UC undergoing cystectomy. Methods: Peripheral blood samples from pts with non-metastatic UC was collected. MDSCs were measured in freshly purified peripheral blood mononuclear cells, using flow cytometry. Total (T) MDSC was defined as CD33+/HLADR-. T-MDSC subtypes were polymorphonuclear (PMN-MDSC: CD15+/CD14-), monocytic (M-MDSC: CD15-/CD14+], and uncommitted (UC-MDSC: CD15-/CD14-]. MDSC populations were presented as % of live nucleated blood cells. Wilcoxon rank sum test was used to compare MDSCs between pCR groups. Kaplan-Meier and log-rank test were used to analyze RFS and OS. Results: MDSC data were available for 124 pts (106 male, 18 female), median age 68, 28 (23%) never smokers, 93 (75%) pure UC. Thirty four pts (27%) received intravesical BCG; 49 (39%) received neoadjuvant chemotherapy (NAC); 22 (19%) had pCR (pT0N0) following surgery. PMN-MDSC was the dominant subtype (42%) and frequency of UC-MDSC and M-MDSC was 40% and 17%, respectively. Circulating levels of T-MDSC and PMN-MDSC were significantly lower in pCR patients than those in non-pCR patients (Table). Sixteen deaths were observed and 21 pts recurred after surgery. The median follow-up time of patients alive was 18.7 months (range 0.3-42.4). The median OS or RFS of all patients was not reached. One-year and two-year OS rates were 94% and 83%, respectively. One-year and two-year RFS rates were 82% and 69%, respectively. There was no association between MDSC subtypes with OS or RFS. Conclusions: Total- and PMN-MDSC subtypes in blood were significantly correlated with pCR in pts with non-metastatic UC who undergo cystectomy. The relatively short follow-up may impact the association with RFS and OS; additional follow-up is needed. [Table: see text]