Abstract 1159: Circulating cell-free DNA (cfDNA) levels and fragmentation patterns discriminate muscle invasive from non-muscle invasive urothelial cancer of the bladder

Purpose: There is risk of clinical under-staging of muscle invasive bladder cancer (MIBC) by trans-urethral resection (TURBT) alone. Circulating biomarkers may improve the staging and pre-treatment risk stratification of patients with bladder cancer by discriminating non-muscle invasive (NMIBC) and MIBC.

Methods: Peripheral blood from 74pts with BC (30NMIBC, 15 MIBC and 29 Met BC was collected in Streck BCT tubes and processed to obtain cfDNA. Total cfDNA quantity (ng/mlof plasma) was assessed by fluorimetry. cfDNA fragment size was measured by Bioanalyzer DNA analysis. Wilcoxon rank sum test, Cochran-armitage trend test, Fisher's exact t-test were used to compare cfDNA quantity and fragmentation pattern (small fragments are indicative of circulating tumor DNA) among pts with NMIBC, MIBC, met BC to predict invasiveness of BC.

Results: There was no significant difference in cfDNA concentration between MIBC and met BC, however, cfDNA levels were significantly lower in pts with NMIBC vs MIBC and met BC. The difference was even more pronounced in case of cfDNA fragment (100-400bp) conc. Total cfDNA (ng/ml) was a good predictor in bladder cancer invasiveness, AUC 0.8 (95% CI 0.7-0.9). The risk of invasion was significantly lower inpatients with total cfDNA &lt 1.5 ng/ml and significantly higher in patients with cfDNA &gt 7.0ng/ml. In 18 pts with cfDNA&lt1.5ng/ml, only 1 pt (5.6%) had invasive cancer (at 1.2). The percent risk of invasive disease was 70.6% for cfDNA concentrations between 1.5-7.0ng/ml and 79.0% for cfDNA &gt 7.0. No invasion was observed among 13 pts with total cfDNA less than 1. This exploratory study suggests that cfDNA levels may correlate with BC stage and hence can be used in juxtaposition with TURBT, exam under anesthesia and CT to better predict clinical staging.

Conclusions: Circulating cfDNA may be a dynamic, low-cost and minimally invasive biomarker that can be used in conjunction with TURBT to predict tumor invasiveness, reduce under-staging, and risk stratify patients for appropriate curative intent therapy.

cfDNA variation with BC stagingcfDNA parametersTotalNMIBCMIBCMET BCp-value(N=74)(N=30)(N=15)(N=29)cfDNA_ng/ml of plasma7.3[2.9,12.5]1.3[0.48,7.4]9.7[4.0,13.3]8.7[6.1,14.4]<0.001bcfDNA fragment (100to400bp)_pg/ml of plasma76.9[0.00,5591.2]0.00[0.00,59.4]3322.7[0.00,8405.2]3344.7[53.8,21930.3]<0.001b

Citation Format: Shinjini Ganguly, Jaleh Fallah, Hong Li, Wei Wei, Aysegul Balyimez, Claudia Marcela Diaz, Pat Rayman, Marcelo Lamenza, Priscilla Dann, Donna Company, Rahul Tendulkar, Jacob Scott, Mohamed Abazeed, Jorge A. Garcia, Moshe C. Ornstein, Brian R. Rini, Byron Lee, Petros Grivas, Omar Mian. Circulating cell-free DNA (cfDNA) levels and fragmentation patterns discriminate muscle invasive from non-muscle invasive urothelial cancer of the bladder [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1159.

Immunological Correlates of Response to Immune Checkpoint Inhibitors in Metastatic Urothelial Carcinoma

BACKGROUND

The identification of prognostic and/or predictive biomarkers for response to immune checkpoint inhibitors (ICI) could help guide treatment decisions.

OBJECTIVE

We assessed changes in programmed cell death-1 (PD1)/PD1 ligand (PDL1) expression in key immunomodulatory cell subsets (myeloid-derived suppressor cells [MDSC]; cytotoxic T lymphocytes [CTL]) following ICI therapy and investigated whether these changes correlated with outcomes in patients with metastatic urothelial carcinoma (mUC).

PATIENTS AND METHODS

Serial peripheral blood samples were collected from ICI-treated mUC patients. Flow cytometry was used to quantify PD1/PDL1 expression on MDSC (CD33⁺HLADR^-) and CTL (CD8⁺CD4^-) from peripheral blood mononuclear cells. MDSC were grouped into monocytic (M)-MDSC (CD14⁺CD15^-), polymorphonuclear (PMN)-MDSC (CD14^-CD15⁺), and immature (I)-MDSC (CD14^-CD15^-). Mixed-model regression and Wilcoxon signed-rank or rank-sum tests were performed to assess post-ICI changes in immune biomarker expression and identify correlations between PD1/PDL1 expression and objective response to ICI.

RESULTS

Of 41 ICI-treated patients, 26 received anti-PDL1 (23 atezolizumab/3 avelumab) and 15 received anti-PD1 (pembrolizumab) therapy. Based on available data, 27.5% had prior intravesical Bacillus Calmette-Guérin therapy, 42% had prior neoadjuvant chemotherapy, and 70% had prior cystectomy or nephroureterectomy. Successive doses of anti-PDL1 correlated with decreased percentage of PDL1⁺ (%PDL1⁺) M-MDSC, while doses of anti-PD1 correlated with decreased %PD1⁺ M- and I-MDSC. Although pre-treatment %PD1⁺ CTL did not predict response, a greater %PD1⁺ CTL within 9 weeks after ICI initiation correlated with objective response.

CONCLUSIONS

Treatment with ICI correlated with distinct changes in PD1/PDL1-expressing peripheral immune cell subsets, which may predict objective response to ICI. Further studies are required to validate immune molecular expression as a prognostic and/or predictive biomarker for long-term outcomes in mUC.

Association of cell-free DNA (cfDNA) levels with myeloid-derived suppressor cells (MDSC) levels in blood of patients (pts) with muscle invasive (MI) and metastatic (met) bladder cancer (BC)

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Background: cfDNA can be detected in healthy individuals but higher concentrations are present in pts with cancer. MDSC are immature immunosuppressive cells that can be mobilized from bone marrow by tumor-related factors. Higher blood MDSC levels have been associated with worse outcomes in pts with solid tumors including BC. We assessed correlations between cfDNA and MDSC levels in pts with MIBC and met BC. Methods: Peripheral blood from pts with MIBC and met BC was collected in Streck BCT tubes and processed to obtain cf nucleic acid extracts. Total cfDNA was determined by fluorimetry. Cell-free DNA fragment size was measured by Bioanalyzer DNA analysis; 100-400 bp fragments (mono- and di-nucleosomal fragments linked to granulocytic processing of apoptotic and necrotic tumor cells) were designated low molecular weight (LMW-frags). The % of MDSC (CD33+/HLADR-) and subtypes were measured. MDSC subtypes were defined as polymorphonuclear (PMN-MDSC: CD15+/CD14-), monocytic (M-MDSC: CD15-/CD14+) and uncommitted (UNC-MDSC: CD15-/CD14-). Spearman’s correlation test was used for analysis. Results: Blood from 37 pts (19% women, 40% never smokers) with MIBC or met BC was collected: 15 (41%) with MIBC and 22 (59%) with met BC at time of collection. There was a significantly positive correlation between total MDSC and cfDNA levels (r = 0.57, P = 0.0003). Among MDSC subtypes, there was a significantly positive correlation between PMN-MDSC and cfDNA levels (r = 0.61, P < 0.0001). The higher level of LMW-frags was significantly but moderately associated with higher total MDSC (r = 0.43, P 0.008) and PMN-MDSC (r = 0.41, P 0.01) levels. There was no significant correlation between cfDNA level and other MDSC subtypes. Conclusions: There was a positive correlation between total and PMN-MDSC with cfDNA levels in blood from pts with MIBC and met BC. That may suggest a putative role for MDSC in mediating cfDNA release into the circulation, consistent with prior reports of granulocyte-mediated ctDNA processing. Further studies need to identify mechanisms and implications of our findings and potential correlation with clinical outcomes.

Circulating cell-free DNA (cfDNA) levels and fragmentation pattern can distinguish nonmuscle invasive (NMI) from muscle-invasive (MI) and metastatic (met) bladder cancer (BC)

4523

Background: Occult MI and met BC may be under-staged. Circulating cfDNA may be a dynamic, low-cost and minimally invasive biomarker. We evaluated correlations between total circulating cfDNA and presence of MIBC and met BC. We hypothesized that the relative abundance of circulating low molecular weight cfDNA would correlate with BC stage. Methods: Peripheral blood from pts with BC was collected in Streck BCT tubes and processed to obtain cf nucleic acid extracts. Total cfDNA quantity (ng/ml) was assessed by fluorimetry. cfDNA fragment size was measured by Bioanalyzer DNA analysis. Wilcoxon rank sum test and Fisher’s Exact test were used to compare cfDNA quantity and fragmentation pattern among pts with NMIBC, MIBC, met BC. Results: Blood was obtained from 58 pts with BC (20% women, 34% never smokers, median age 71 (29-89). There was no significant difference in cfDNA between MIBC and met BC, however, it was significantly lower in pts with NMIBC vs MIBC and met BC (table). The concentration of low molecular weight fragments (LMW-frags) (100 - 400) base pairs and the ratio of LMW-Frag to cfDNA were significantly different between pts with NMIBC and pts with MIBC or met BC (table). Using median values as the cutoff, there was a significantly higher proportion of pts with cfDNA > 7 ng/ml and LMW-frags > 1.6 ng/mL, in MIBC & met BC vs NMIBC (p < 0.001). The % of pts with LMW-frags to cfDNA > 30%, was significantly different among NMIBC, MIBC and met BC groups: 16%, 53%, 78%, respectively (p < 0.001). Conclusions: This exploratory study suggests that cfDNA levels may correlate with BC stage. Measuring the relative abundance of LMW-frags with the expected size of cf DNA can enhance the specificity of cfDNA analysis for distinction between MIBC and met BC. Further studies are needed to confirm findings and define the optimal cut-points for optimal BC staging. [Table: see text]

Blood myeloid derived suppressor cells (MDSC) in metastatic urothelial carcinoma (mUC) are correlated with neutrophil-to-lymphocyte ratio (NLR) and overall survival (OS)

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Background: MDSC have been linked to the chronic inflammatory microenvironment of tumor cells and pathologic outcomes in UC patients (pts) undergoing cystectomy. NLR is an established inflammatory biomarker with prognostic properties in mUC. We hypothesized that MDSCs correlate with NLR and OS in mUC. Methods: MDSCs were measured in blood samples from mUC patients by fresh unfractionated whole blood (WB) and peripheral blood mononuclear cells (PBMC). MDSCs were identified by flow cytometry in WB and defined as LinloCD33+/HLADR- (Total MDSC). MDSC subsets were defined as 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 from PB and absolute numbers from WB. Spearman’s correlation assessed correlations between MDSC & NLR. Kaplan Meier curves and log rank test estimated OS from the time of MDSC collection to last follow up or date of death. Results: Of 79 pts, 77% were men and 42% were never smokers with a median age of 69 (31-83). Overall, 71% had pure UC and 81% had lower tract UC. Prior therapies include intravesical therapy (22%), neoadjuvant chemotherapy (31%), and cystectomy/nephroureterectomy (61%). Median follow up was 12 months (range: 0.6-36.5). PMN-MDSC was the predominant subset in WB and PBMC. There was significant correlation between individual MDSC subsets in WB and PBMC (p≤0.001). Negative correlation was noted between NLR and WB UC-MDSC:PMN-MDSC ratios (rho = -0.27, p = 0.03), as well as NLR and PB UC-MDSC:PMN-MDSC (rho = -0.28, p = 0.02). Median survival was 17.7 months (95% CI: 11.0-NA months). Overall 1-yr and 3-yr survival were 0.60 (95% CI: 0.49-0.73) and 0.15 (95% CI: 0.03-0.67), respectively. Higher WB UC-MDSC levels were associated with shorter OS (HR 2.85, 95% CI: 1.43-5.65, p = 0.003). Conclusions: Specific MDSC subsets correlate with NLR. Higher WB UC-MDSC levels have negative prognostic roles for OS. Given the feasibility of serial blood draws, dynamic assessment of MDSC over time and further validation with longer follow up are needed.

Immunological correlates of response to immune checkpoint inhibitors (ICI) in metastatic urothelial carcinoma (mUC) patients (pts)

454

Background: Identification of biomarkers predictive of response to ICI could help guide treatment (tx) decisions. We assessed the correlation between PD1/PDL1 expression in key immunomodulatory subsets (myeloid-derived suppressor cells [MDSC]; CD8+ T cells) and tx response in mUC pts treated with ICI. Methods: Serial peripheral blood samples were collected from mUC pts treated with ICI. Flow cytometry was used to quantify PD1/PDL1 expression in MDSC (CD33+HLADR−) and CD8+ T cells (CD8+CD4−) from live peripheral blood mononuclear cells. MDSC were subdivided into monocytic (M)-MDSC (CD14+CD15−), polymorphonuclear (PMN)-MDSC (CD14− CD15+), and immature (I)-MDSC (CD14− CD15−). Mixed-model regression and Wilcoxon rank-sum tests were performed to assess post-ICI changes in immune marker expression and identify correlations between PD1/PDL1 expression and best overall response (BOR) to ICI. Results: Of 36 ICI-treated pts with ≥2 blood samples, 24 received anti-PDL1 (22 atezolizumab/2 avelumab; [A]) and 12 received anti-PD1 (pembrolizumab [P]). 78% were men, median age 69 (46–81), 28% never smokers, 19% had prior intravesical BCG, 39% prior neoadjuvant chemotherapy, and 64% prior cystectomy. BOR to ICI included 3 PR/14 SD/7 PD (A) and 1 CR/2 PR/6 SD/3 PD (P). Successive doses of A correlated with decreased %PDL1+ M-MDSC (mean change −5.26/dose; p = 0.009), while those of P correlated with decreased %PD1+ M- and I- MDSC (mean change −1.55 and −1.14/dose; p = 0.04 and 0.02, respectively). Though pre-tx %PD1+ CD8+ T cells did not predict BOR, greater PD1 expression by CD8+ T cells within 12 weeks after ICI initiation correlated with BOR (Table). Conclusions: ICI tx correlated with distinct changes in PD1/PDL1 expression by specific peripheral immune cell subsets. Responders to ICI had higher % of PD1+ CD8+ T cells after ICI than non-responders, though pre-tx % were comparable between groups. Further validation of these and other potential blood/tissue biomarkers is ongoing. [Table: see text]

Serial changes in PD1/PDL1 expression in metastatic urothelial carcinoma (mUC) patients (pts) treated with immune checkpoint blockade (CPB)

109

Background: Since CPB may alter immune marker expression in key immunomodulatory populations such as myeloid-derived suppressor cells (MDSC) and CD8+ cytotoxic T lymphocytes (CTL), we evaluated PD1/PDL1 expression in longitudinal samples from mUC pts treated with CPB. Methods: Serial peripheral blood samples were collected from mUC pts who received CPB. PD1/PDL1 and VISTA expression was measured in MDSC (CD33+HLADR−) and CTL (CD8+CD4−) from live peripheral blood mononuclear cells using flow cytometry. MDSC subsets were further defined as (G)ranulocytic (CD15+CD14−), (M)onocytic (CD15−CD14+), and (I)mmature (CD15−CD14−). PD1/PDL1 and VISTA expression was presented as % of each MDSC subset or CTL. Wilcoxon signed-rank tests and mixed-model regression analyses were performed to assess changes in immune marker expression after CPB. Results: Of 30 CPB-treated pts with ≥ 2 blood samples for analysis, 21 received anti-PDL1 (20 atezolizumab/1 avelumab; [A]) and 9 received anti-PD1 (pembrolizumab [P]). Median age at diagnosis was 69.5 (46–81), 77% men, 33% never smokers, 63% pure UC, 70% bladder primary, 20% prior intravesical BCG, 37% prior neoadjuvant chemotherapy, 63% prior cystectomy. Best overall responses to CPB were 3 PR/13 SD/5 PD (A) and 1 CR/1 PR/4 SD/3 PD (P). Successive doses of A correlated with decreased %PDL1+ M-MDSC, while those of P correlated with decreased %PD1+ M- and I- MDSC (Table). No significant changes in VISTA expression were detected. In 11 A-treated pts with samples before/after the 1st dose, %PDL1+ M- and I- MDSC decreased (median change −25.5 and −5.7; p = 0.02 and 0.03) and %PD1+ CTL increased (median change +2.4; p = 0.02) between 1st and 2nd samples. Conclusions: In this mUC pt cohort, distinct post-tx changes in %PD1/PDL1 in MDSC subsets and CTL occurred based on CPB (anti-PD1 vs anti-PDL1). Further analysis of correlations between CPB, immune marker expression, clinicopathologic factors, and outcomes is ongoing in a larger cohort. Mean absolute change in marker expression per dose in pts treated with CPB. [Table: see text]

Serial measurements of myeloid derived suppressor cells (MDSC) in metastatic urothelial carcinoma (mUC) patients (pts) treated with immune checkpoint inhibitors (CI)

e16005

Background: MDSC are a heterogeneous population of immunosuppressive cells with potentially predictive implications in UC pts receiving CI. We hypothesized that MDSC populations may change after CI exposure. Methods: Serial peripheral blood samples were collected from mUC pts treated with CI. MDSC were measured in fresh unfractionated whole blood (WB) and in peripheral blood mononuclear cells (PBMC). MDSC were identified by flow cytometry in WB and defined as LinloCD33+/HLADR- [(T)otal MDSC]. MDSC subsets were defined as (G)ranulocytic (CD15+CD14-), (M)onocytic (CD15-CD14+), (I)mmature (CD15-CD14-), or CD11b+. MDSC populations were presented as % of live nucleated blood cells and as absolute numbers from WB. The Wilcoxon signed rank and rank sum tests were used to assess changes in MDSC populations while on CI. Results: 17 pts treated with CI (9 atezolizumab [A], 8 pembrolizumab [P]) had ≥ 2 MDSC samples for analysis. Median age at diagnosis was 71 (46-81), 12 men, 29% never smokers; 53% / 29% / 18% ECOG PS 0/1/2 and 59% visceral metastasis at the time of 1st sample collection. 10 pts received CI as 1st line therapy (Tx) in metastatic setting; 7 pts received chemotherapy as 1st-line Tx for mUC (6 platinum-based, 1 docetaxel) and CI as 2nd-line Tx. In 16 pts with samples before 1stdose, there was a relative decrease (median 36.3%, range -59.7 to +21.2) in PBMC % I-MDSCs between 1st and 2nd samples (p=0.06). Interestingly, PBMC %M-MDSC and %I-MDSC tended to increase compared to baseline in pts treated with P, while they tended to decrease in pts treated with A (Table). Conclusions: In this cohort of pts with mUC treated with CIs,MDSC changes differed based on CI (anti-PDL1 or anti-PD1). Further study in larger cohort with various prior Tx lines and longer follow up as well as correlations with Tx response, toxicity and outcomes are ongoing. [Table: see text]

Real-world experience with atezolizumab (atezo) in advanced urothelial cancer (UC)

e16031

Background: Atezo was recently FDA-approved for patients (pts) with UC (IMvigor210 trial). We assessed the safety and efficacy of Atezo in the real world setting and explored the role of putative biomarkers. Methods: Data from 44 consecutive non-trial pts with UC treated with ≥1 dose of Atezo 1200mg IV q3w at Cleveland Clinic (May - Dec 2016) were available. Demographic, clinicopathologic, biomarker data, including blood neutrophil to lymphocyte ratio (NLR) and myeloid derived suppressor cell (MDSC) populations [LinloCD33+/HLADR-(Total), and Granulocytic(CD15+CD14-), Monocytic(CD15-CD14+), Immature(CD15-CD14-), CD11b+ subsets], were collected. Response, progression-free survival (PFS) and overall survival (OS) were measured (RECIST v1.1). Adverse events (AE) were reported (CTCAE v4.03). Outcome data were analyzed with Fisher’s exact test, chi-square tests, log rank test and proportional hazards models. Results: Median age was 68y (34-88), 68% men, 68% pure urothelial histology, 27% never smokers; 61% PS > 0, 61% visceral metastases, 57% CrCl < 60 mL/min, 84% bladder primary, 61% prior cystectomy. In metastatic setting, 25% had ≥2 prior systemic therapies, 84% prior platinum-based regimen, and 9% no prior therapy. With median follow-up of 3.3 months ( < 1 - 6.6) and median number of 3 doses, in 38 pts evaluable for response, 21% had PR; 24% SD; 61% progressed, 27% died; estimated median (m)PFS was 3 months (95%CI 2.2 - 4.3) and mOS was 5.2 months (95%CI 4.6 - NR). Only 3/27 eligible pts got subsequent treatment. Number of metastatic sites, 2 Bellmunt prognostic factors, and NLR ≥ 5.0 negatively impacted response, PFS and OS. MDSC populations (data available in 14 pts) demonstrated non-significant correlation with worse outcome and elevated NLR. Most frequent all-cause AE ( > 20%) were fatigue (60%, G3:9%), anorexia (33%, G3:7%), elevated creatinine (26%, G3:5%); 1 pt had G4 hyperbilirubinemia. There were no treatment-related deaths. Conclusions: To our knowledge, this is the largest real-world experience with Atezo in UC. Response and toxicity were comparable to IMvigor210 trial; estimated mOS was shorter but with limited follow up. Higher NLR had negative prognostic value, while the role of MDSCs merits further exploration.

Myeloid derived suppressor cells (MDSC) and inflammatory biomarkers in metastatic urothelial carcinoma (mUC)

4548

Background: MDSC are potent immunosuppressive cells with prognostic implications in many solid tumors. We previously reported significant correlations between MDSC and clinicopathologic features in localized UC. We hypothesized that different MDSC populations may correlate with inflammatory biomarkers and clinicopathologic features in mUC. Methods: Peripheral blood samples were collected from 46 mUC pts. MDSCs were measured in fresh unfractionated whole blood (WB) and in peripheral blood mononuclear cells (PBMC). MDSCs were identified by flow cytometry in WB and defined as LinloCD33+/HLADR- [(T)otal MDSC]. MDSC subsets were defined as (G)ranulocytic (CD15+CD14-), (M)onocytic (CD15-CD14+), (I)mmature (CD15-CD14-), or 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. Results: Of 46 pts:78% men, median age at diagnosis 69 (31-83), 33% never smokers, 76% pure UC, 76% bladder primary, 28% prior intravesical therapy, 35% prior neoadjuvant chemotherapy, 56% prior cystectomy, 83% overweight/obese. G-MDSC was the predominant subset in WB (43%) and PBMC (39%), although M-MDSC were almost equally predominant in PBMC (35%). There was a correlation between the WB and PBMC values of T-, I-, and M- MDSC (p≤0.05). Higher % WB I-MDSC correlated with lower blood neutrophil/lymphocyte ratio (NLR) (p = 0.009), while higher WB G-MDSC and %PBMC G-MDSC were associated with higher NLR (p = 0.03 and p = 0.02, respectively). Higher I-MDSC / G-MDSC ratio was associated with lower NLR (r = -0.35, p = .02) and with various clinicopathologic parameters. Conclusions: HigherI-MDSC / G-MDSC ratio correlates inversely with NLR, which is considered an inflammatory biomarker and had prognostic value in other studies. The mechanism of MDSC interaction with inflammatory response in mUC pts merits evaluation and is being investigated in a larger cohort of UC pts on chemotherapy or immunotherapy (with longer follow up).

Intra-patient heterogeneity in urothelial cancer (UC) circulating tumor cells (CTC) and PDL1 expression to identify biomarkers of response and new therapeutic targets: A pilot study

4537

Background: Recent use of immune checkpoint inhibitors (CI) has improved overall survival (OS) in a subset of patients (pts) with metastatic UC. Intra-patient tumoral heterogeneity and epithelial-to-mesenchymal transition has been hypothesized as a driver of treatment resistance to both chemotherapy and CI in UC. There is a critical need to evaluate heterogeneity in UC for biomarkers of treatment response and new therapeutic targets. Trop2 is hypothesized to play a role in UC progression and is the target of a new antibody-drug conjugate, IMMU-132 that is being tested in UC trials. We report the phenotypic comparison of PDL1 expression among CTC subpopulations in UC pts. Methods: Peripheral blood samples were collected from pts with UC treated at Cleveland Clinic and U. of Wisconsin. Immunomagnetic capture and CTC enumeration using both EpCAM and Trop2 from matched blood samples was performed in the VERSA platform. Protein expression for PDL1 in these CTC populations was quantified. Longitudinal analysis of UC pts treated with chemotherapy or CI is ongoing. Results: CTC were captured using EpCAM and Trop2 in all 10 pts in our initial cohort. The frequency of Trop2 CTC was higher than EpCAM CTC with a mean of 248 Trop2 CTC (range 2-1885) compared to 76 EpCAM CTC (range 1-632). PDL1 expression was more frequent in Trop2 CTC than EpCAM CTC. In two pts progressing on Atezolizumab, Trop2 CTC had a higher frequency of PDL1 expression compared to EpCAM CTC (85% vs 2% in pt 1 and 2% vs 0% in pt 2). In pts followed longitudinally, Trop2 CTC dropped from 1885 to 1 in a pt with response to Atezolizumab and PDL1+ CTC declined from 4 to 0. After 1 cycle of Carbo/Gem in another pt, EpCAM CTC declined from 46 to 3 while Trop2 CTC from 116 to 47. Conclusions: This is the first report of CTC heterogeneity in pts with UC identifying high frequency of Trop2 CTCs with variable expression of PDL1 across different pts. Early results from longitudinal analysis suggest CTC as potential predictive / pharmacodynamic biomarkers of treatment response. Prospective data validation in larger cohort is ongoing, while IMMU-132 clinical trials in UC may provide context for future validation.

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

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]

Correlation of myeloid derived suppressor cell (MDSC) populations with clinicopathologic features in urothelial carcinoma (UC)

434

Background: MDSC are a heterogeneous population of potent immunosuppressive cells with potential predictive/prognostic significance in solid tumors. The association between MDSC and clinicopathologic features in patients (pts) with UC was investigated. Methods: Peripheral blood from 26 non-metastatic UC pts scheduled to undergo cystectomy or nephroureterectomy at Cleveland Clinic was collected. MDSC were enumerated in fresh unfractionated blood (WB) and in peripheral blood mononuclear cells (PBMC). (T)otal MDSC were defined as CD33+/HLADR-; out of T-MDSC, (G)ranulocytic (CD15+CD14-), (M)onocytic (CD15-CD14+) and (I)mmature (CD15-CD14-) MDSC were identified. CD11b MDSC (Linlo/HLADR-/CD33+/CD11b+) were identified in WB. MDSC populations were presented as % of live nucleated blood cells and as absolute numbers from WB. Wilcoxon rank sum test was used to assess associations between MDSC populations and clinicopathologic features. Due to the exploratory nature of the study, p < .10 was considered significant. Results: Of 26 pts, 25 had surgery and 1 is under surveillance. 24 had both WB and PBMC data. 23/26 were men; median age 67. Of 26 pts, all had primarily UC histology; 7 had mixed UC histology, 11 had prior intravesical BCG, 12 neoadjuvant therapy (10 Gem/Cis, 1 Gem/Carbo, 1 unknown). Of 25 pts who had surgery, 5 had pT3/4 stage; 5 had LVI; 9 had CIS. All but 1 had negative LN. Higher levels of specific WB MDSC populations were associated with mixed histology (including squamous), CIS, and higher pT-stage (Table). When compared to a separate cohort of 11 pts with metastatic UC, the % G-MDSC in PBMC was lower in non-metastatic pts (median 0.3 vs. 1.47; p = .05). Conclusions: Although no single MDSC population correlated with all the evaluated clinicopathologic features, higher levels of certain MDSC populations appear to correlate with histology and pT stage. Further validation of blood and tissue is ongoing in a larger cohort. [Table: see text]