Citations

695 Background: Small cell carcinoma of the bladder (SCCB) is a rare variant of bladder cancer with limited data informing prognosis. We present a novel prognostic model for disease specific survival (DSS) for patients with non-metastatic (M0) SCCB, derived from the Surveillance, Epidemiology and End Results (SEER) database. Methods: The SEER database (18 registries/November 2020) was queried with the ICD-10 topography codes C67.0-C67.9 (bladder), and the morphologic code 8041 (SCCB). Eligible patients (adults, histologic confirmation, available follow-up/staging data, M0) were randomly divided into a training (TC) and a validation cohort (VC) (7:3 ratio). Variables significantly associated with DSS were identified with multivariate Cox regression and backwards stepwise conditional approach and inserted in the model. Points were assigned to each variable based on the formula: Probability of an event at time t=S0(t)exp(β1x1, β2x2...), (β = regression coefficients, x = observed covariate values, S0(t) = survival function). Cumulative risk points were assigned to each patient and three distinct risk categories for DSS were constructed. Harrel’s C-statistic with bootstrap resampling was used for internal (TC) and external (VC) validation. Model performance was compared to the AJCC 8th edition (likelihood ratio test -LRT). Results: A total of 1039 patients were included (739 TC, 300 VC). No statistically significant differences in baseline characteristics/survival outcomes were identified between TC and VC. Age (years), T/N stage, radical cystectomy, chemotherapy, and radiation were significant variables inserted in the multivariate model (table). Patients were stratified to three risk groups (low, intermediate, high) based on the total cumulative risk points collected. Median DSS was NR (95%CI; NR, NR), 25 (95% CI; 18-32) and 9 months (95% CI; 7-11) for the low, intermediate, and high-risk category, log-rank p<.001. Harrel's C-statistic for the model was 0.70 (95%CI;0.67-0.73) in the TC and 0.66 (95%CI; 0.61-0.71) in the VC. In comparison, C-statistic for the AJCC 8th edition was 0.56 (95% CI; 0.52-0.59) and 0.53 (95% CI; 0.51 to 0.57), respectively. The LRT demonstrated superior performance of the model compared to AJCC (p<.001). Conclusions: We present a novel prognostic model for DSS in patients with locoregional SCCB composed of variables readily available in daily practice, which may serve as a useful tool for individualized risk assessment of patients with this rare malignancy. Further validation in prospective studies/clinical trials is warranted. [Table: see text]

686 Background: Immune checkpoint inhibitors (ICI) have been used to treat advanced muscle invasive and/or metastatic bladder cancer. However, ICIs are only effective in 30-40% of cases. In light of potentially significant IRAE’s, tools to predict individual patient level benefits are desirable. AI technology offers the opportunity to apply computational methods to predict outcomes from readily available digitized pathology slides. We investigated the utility of an AI platform integrating computational biomarkers based on morphological characterization of digitized H&E slide whole images (WSI) to predict response to ICI. Methods: We analyzed H&E-stained whole slide images (WSI) of bladder tumor tissue collected from transurethral resection of bladder tumor (TURBT) from 116 patients with advanced or metastatic bladder cancer at a single institution between 2015-2020. Adjacent multiplex IHC stained specimens were analyzed myeloid and lymphoid marker panels. 20 patients from the overall cohort treated with ICI were designated ‘responders’ (complete response, partial response, stable disease) and 20 patients were identified as non-responders (progressive disease) based on ICI best clinical/radiographic response. WSIs were divided into small non-overlapping image patches. These image tiles were processed into multiple AI encoder models to extract morphological features. The tile morphological features, represented by high dimensional vectors, were combined by an aggregation model to represent the whole slide morphology and then used to classify the patients into responders vs non-responders to immunotherapy. Area-under-the-receiver operating characteristic (AUC) was used to measure the performance of response prediction. Results: Our method shows AUC of 0.708 at classification of the patients (n=40) into responder and non-responder groups. With a cutoff that identifies the top 50% patients (n=20) of high probability of responding to immunotherapy predicted by our models, 75% of them are responders. In the bottom 50% patients (n=20) of the low scores, 75% of them are non-responders. . Multiplex IHC (myeloid and lymphoid panel) was performed using adjacent sections and were characterized yielding deeper mechanistic insight into the inflammatory populations driving predictive morphologic patterns. Conclusions: By applying innovative AI morphological analysis on patient WSIs, we generated a computational biomarker that shows promising ability to predict patient response to immunotherapy in bladder cancer. This approach merits future prospective validation and additional patient level analysis in broader cohorts. [Table: see text]

654 Background: MSI and TMB correlate with ICI efficacy. We assessed the association between TMB and MSI with outcomes in pts with aUC treated with anti-PD1/L1 in a ‘real-world’ cohort. We hypothesize that pts with high TMB and MSI-high (H) have better outcomes with ICI. Methods: In this retrospective study we included pts from 13 sites treated with ICI for aUC. We calculated overall response rate (ORR), median overall and progression-free survival (mOS, mPFS) using KM method from ICI start. TMB and MSI were assessed by NGS. TMB was analyzed as dichotomous (≥10 vs <10 mut/Mb) and continuous variable. The analysis was stratified by therapy line (1L/upfront, 2+L). Multivariable models were adjusted by Khaki factors for 1L/upfront and Bellmunt factors for 2+L. We separately analyzed pts on maintenance avelumab (mAV). MSI is reported with descriptive statistics only. Results: 342 pts were treated with ICI 1L/upfront or 2+L (69% pure UC, median age at ICI start 69, 77% men, 90% White, 16% upper tract primary, 12% liver metastases [mets], 78% ECOG PS 0-1). Median f/u from ICI start was 34 months (mo). ORR was 36% (95%CI 26-46%) in pts with TMB≥10 vs 30% (95%CI 23-36%) with TMB<10 (OR=1.4 [95%CI 0.8-2.5] p=0.3). ORR was 75% (6/8) in pts with MSI-H and 30% (60/200) with MSI stable (MSI-S). mPFS was similar between TMB≥10 and <10 groups (6 vs 4 mo; HR=0.88 [95%CI 0.61-1.26] p=0.48) and between MSI-H and MSI-S (5 mo). mOS was numerically longer (not significant) in pts with TMB≥10 vs TMB<10: 25 vs 21 mo; (HR=0.7 [95%CI 0.50-1.09] p=0.12) and with MSI-H and MSI-S (NR and 20 mo). A significant association was found between TMB (continuous variable) and OS (HR=0.97 [95%CI 0.95-0.99] p=0.01). TMB analyses by therapy line are shown in Table. In the 1L/upfront setting (N=144), ORR 71% (5/7) vs 33% (45/135), mPFS 5 and 4 mo, mOS NR and 22 mo for MSI-H and MSI-S, respectively. Pts on mAV (n=77) were 77% men, 92% White, 16% upper primary, 13% liver mets, 84% ECOG PS 0-1 with median f/u 15 mo from avelumab start; mOS was NR for MSI-H and 24 mo for MSI-S; mPFS was 4 mo for both groups. Of 3 pts on mAV with MSI-H: 1 CR, 2 SD; of 58 pts with MSI-S: 4CR, 4PR, 24 SD, 21 PD, 5 unknown. Conclusions: MSI-H had numerically higher ORR and higher TMB was associated with longer OS with ICI, but further validation is needed. Limitations: retrospective design, small sample size for MSI-H cases, lack of randomization and central scan review, selection/confounding. [Table: see text]

643 Background: The FDA approval of enfortumab (EV) and pembrolizumab (Pembro) combination therapy as a first-line treatment for cisplatin-ineligible patients with locally advanced/metastatic urothelial carcinoma (la/mUC) was based on the EV-103 trial. We aim to assess the clinical response rate of this combination therapy in our institution's patients with locally advanced and metastatic UC. Methods: This retrospective cohort study included 20 patients diagnosed with locally advanced/metastatic UC(la/mUC) who were treated with EV-Pembro combination for at least 2 cycles, from June 2022 to August 2023 at the Mayo Clinic. Patients who were treatment naïve or who progressed one or more lines of therapy were included in the study cohort. Main outcome of interest included imaging-based best overall response rate in terms of complete (CR) and partial (PR) response, stable disease (SD), and progressive disease (PD). Results: Out of 20 patients, the number of males and females were 16 (80%) and 4 (20%) respectively; the median age was 77 years (IQR: 51-92). 3 (15%) of patients had involvement of upper urinary tract disease along with bladder cancer. The common sites of visceral metastasis at the time of initial presentation include liver 2(10%), lung 6(30%) and lymph nodes12(60%). Common toxicities of this regimen included rash, pruritis, peripheral neuropathy, fatigue, transaminitis, dysgeusia, and diarrhea. The treatment was stopped in 10 (50%) patients due to completion of planned therapy (achieved CR or proceeded with resection of residual disease) (30%), 5 patients due to progression (50%), 1 patient due to therapy side effects (10%) and in 1 patient due to death (10%). The objective response was 45% (N =9); 5 (25%) had PR, and 4 (20%) had CR. A total of 2 (10%) had SD while 2 (10%) experienced PD. Histological correlation with clinical benefit is shown in the table. Conclusions: EV-Pembro combination therapy shows promising responses in patients who have progressed after previous lines of therapy, consistent with previously published data on EV 201 in small cohorts. However, ongoing expansion of this cohort and data from larger studies will help further elucidate survival benefits and their correlation with genetic testing. [Table: see text]

642 Background: Perioperative blood transfusion has been reported in up to 60% of patients undergoing RC. Unfortunately, perioperative blood transfusion in patient undergoing RC has been associated with poor oncological outcomes. Tranexamic acid (TXA) use has been proposed to decrease the need for perioperative blood transfusion. Here we seek to investigate the impact of intraoperative TXA on survival outcomes in patients undergoing radical cystectomy (RC) for bladder cancer. Methods: We queried the prospectively maintained Mayo Clinic Radical Cystectomy registry and identified all RC performed for bladder cancer between 1990-2021. Primary outcomes were patient’s overall survival and cancer specific survival among patients who received TXA versus patients who did not receive TXA. Results: Among 2929 patients who underwent RC in our institution between 1990-2021, 468 received TXA (IV) intraoperatively (Group A) and were propensity score matched 1:1 for age, neoadjuvant chemotherapy, adjuvant chemotherapy, pT stage, pN stage, and preoperative hemoglobin with a group who did not receive TXA (Group B, n= 468). At 8 years followup, 61% of patients who received TXA were alive versus 46% of patients who did not receive TXA. In univariable and multivariable analyses of factors associated with CSS (Table1), node positive disease, pT2-T4, peri-operative blood transfusion were associated with poor survival outcomes. While use of TXA was associated with improved CSS outcomes. Conclusions: In our study, TXA use in patients undergoing radical cystectomy was associated with decreased risk or peri-operative transfusion, improved patient’s overall survival, and cancer specific survival. We can’t explain the biological rational for improved survival however these findings warrant further prospective investigation. [Table: see text]

641 Background: Perioperative blood transfusion is associated with an increased risk of adverse events and tranexamic acid (TXA) use has been proposed to decrease the need for perioperative blood transfusion. Herein, we seek to investigate the impact of intraoperative TXA on perioperative risk of VTE in a subset of patients who underwent robotic-assisted radical cystectomy (RARC) for bladder cancer. Methods: We queried the prospectively maintained Mayo Clinic Radical Cystectomy registry and identified patients who underwent RARC between 2004-2021 and received TXA intraoperatively. In univariable and multivariable analyses, we investigated factors associated with bleeding and VTE within 30 days post-operatively. Results: Of 2862 patients, we identified 94 patients who received TXA (IV) intraoperatively (Group A) and were propensity score matched 1:1 for age, neoadjuvant chemotherapy, pT stage, pN stage, and preoperative hemoglobin with a group who did not receive TXA; 38 patients (Group B). In univariable and multivariable models, use of TXA has no statistically significant impact on patient’s risk of bleeding or VTE. In a univariable model, number of positive lymph nodes and extent of lymph node dissection were associated with increased risk of VTE (Table 1). Conclusions: In our study, use of TXA in patient’s undergoing RARC was safe and was not associated with increased risk of VTE. [Table: see text]

639 Background: Immunotherapy combined with chemotherapy (IO/C) as the first-line management of locally advanced or metastatic urothelial carcinoma (LA/mUC) has been investigated in multiple trials with conflicting outcomes. Therefore, we conducted a meta-analysis of available trials to compare objective response rates (ORR) of this combination regimen, both in overall and in cisplatin-ineligible populations. Methods: EMABSE and MEDLINE were searched from 2000 through July 20th, 2023, to identify phase II and III clinical trials assessing IO, C or both in LA/mUC. Main outcome of interest was objective response rates (ORR) as defined in the included trials. An inverse variance random-effects meta-analysis was performed to estimate pooled ORR using the restricted maximum likelihood estimation method. Subgroup differences were assessed among IO/C, IO alone, and C alone. The threshold for statistical significance was established at 0.1. Results: Of 5975 citations identified, a total of 26 trials with a total of 4,628 participants were included in this systematic review. In the overall group, the ORR in IO/C trials (5 trials, 1,236 patients) was 44.70% (95% CI: 21.88%- 70.0%). In IO trials (7 trials, 2,189 patients), ORR was 23.68% (19.55%- 28.36%) and in C trials (26 trials, 4,628 patients) was 43.46% (37.43%-49.68%]). In the cisplatin-ineligible group, the ORR in IO/C trials (2 trials, 240 patients) was 60.06% (33.38%-81.86%), in IO trials (6 trials, 1,103 patients) was 26.15% (23.01%; 29.56%), and in C trials (8 trials, 767 patients) was 42.45% (35.67%-49.52%). In terms of subgroup differences, the difference in ORR was statistically significant between IO/C and IO trials (p= 0.0844) and between IO and chemotherapy trials (p< 0.0001) in the overall population. Similarly, we found a statistically significant difference in ORR between IO/C and IO (p= 0.0108) and between IO and chemotherapy trials (p< 0.0001) in the cisplatin-ineligible population. No statistically significant differences were observed between IO/C and C alone. Conclusions: First-line IO/C may achieve a better objective response compared to IO alone in patients diagnosed with locally advanced/metastatic UC. Although, there appears to be a trend of greater benefit with IO/C compared to C alone, the difference was not statistically significant. The results will be updated as soon data from new trials (CheckMate 901 and EV 302) becomes available which could offer new insights. [Table: see text]

627 Background: Enfortumab vedotin (EV) is an antibody-drug conjugate recently approved to treat locally advanced or metastatic bladder cancer (la/mUC). Initial trials have shown promising response to EV in advanced urothelial cancers (UC), where prognosis is currently poor. Here, we report real-world experience using EV at a tertiary center. Methods: This study reports treatment details and outcomes in 92 patients (pts) that received at least one complete cycle of EV monotherapy in treatment of la/mUC. Treatment details include intent of cycle duration, 21 days (treatment on days 1 and 8) or 28 days (treatment on days 1, 8 and 15), dose reductions, and median number of cycles completed. Interruptions in treatment are reported as intentional (i.e. holding EV after achieving positive response) or unintentional (i.e. secondary to drug toxicity or other delay). Image-based best clinical response consists of progressive disease (PD), stable (SD), partial (PR), complete response (CR), and not evaluable (NE). Clinical benefit rate (CBR) is defined as either SD, PR, and CR outcomes. The Kaplan-Meier method was used to estimate overall survival (OS) and progression-free survival (PFS). Results: Patients mean age was 71.1 years (IQR: 66.8 - 78), 72 (79.2%) are male and 20 (20.8%) female, 89 (96.7%) pts received EV in the setting of metastatic UC, 3 (3.3%) in locally advanced UC. 13 (13.5%) pts were previously chemotherapy exposed, 9 (9.8%) were immunotherapy exposed, 60 (65.2%) were both chemo and immunotherapy exposed, and 11 (12.0%) received EV first line. 46 (50%) pts underwent 21-day treatment cycles, and 46 underwent 28-day treatment cycles. The median number of EV cycles was 3 (range 1-16) in the overall cohort, 3 in the 21-day cycle group, and 4 in the 28-day cycle group. 50 (54.3%) pts required dose reductions secondary to toxicity. 11 (12.0%) pts had planned interruptions, and 33 (35.9%) had unplanned interruptions. Best clinical response consisted of 24 (26.0%) pts with PD, 12 (13.0%) with SD, 25 (27.2%) with PR, 17 (18.5%) with CR, and 14 (15.2%) NE. CBR was 54 (58.7%) in the overall sample. CBR in the 21-day and 28-day cycle groups was identical at 27 (29.3%). EV therapy was discontinued most for cancer progression (34, 37.0%), therapy toxicity (18, 19.6%), and pt death (12, 13.0%). In 13 (14.1%) pts therapy is still ongoing. 73 (76.0%) pts had mild to moderate toxicities, and 19 (19.7%) reported severe toxicities that required hospitalization. Median OS in the total cohort was 11.01 months (95% CI: 8.51-14.6). Median PFS is 5.49 months (95% CI: 4.60-8.19). Conclusions: Real-world utilization of EV showed significant heterogeneity in administration patterns (21 days vs 28 days) and across a range of settings (first line, chemo exposed, IO exposed, chemo and IO exposed). Although EV has high response rates, more than 3/4th of patients suffered mild to moderate toxicities and 1/5th required hospitalization.

601 Background: Neuroendocrine carcinomas (NEC) of the genitourinary (GU) tract, including small cell (SC) NEC and large cell (LC) NEC, are rare aggressive malignancies. Although highly sensitive to cisplatin-based chemotherapy, GU metastatic NEC (mNEC) have limited data to support next therapies. Lurbinectedin, a marine-derived alkylating drug and a selective inhibitor of oncogenic transcription and DNA repair pathways, is FDA-approved for small cell lung cancer (SCLC) after progression on frontline platinum-based therapy, with a disease control rate (DCR) of 68.6%. It is unknown whether DCR is similar in SCLC and GU mNEC. Methods: We report the first multi-institutional series (n=14) of lurbinectedin in GU mNEC. Imaging-based best overall responses (BOR) were noted as complete (CR), partial (PR), stable (SD), progressive (PD) or non-evaluable (NE). DCR includes CR, PR, and SD. We use the Kaplan-Meier method for overall survival (OS) and progression-free survival (PFS) from lurbinectedin start date. We define duration of response (DoR) from response date to progression or last contact date for patients (pts) with CR or PR. Results: Most pts had a median age at metastasis of 70.5 years (ICR: 64-74.5) [Table]. Primary locations were bladder (7/14, 50%), prostate (5/14, 35.7%) and ureter (2/14, 12.3%). Histology at diagnosis mostly consisted of mixed or pure SCNEC, with one exception of LCNEC. Most pts had visceral disease, prior immunotherapy and at least 2 prior lines of therapy for mNEC before lurbinectedin (8/14, 57.1%). DCR was 6/14 (42.8%), including 5 bladder pts and 1 prostate pt. Among bladder pts, BOR included one CR (1/7, 14.3%) for the LCNEC case, 2 PR (2/7, 28.6%), 2 SD (2/7, 28.6%) and 2 PD (2/7, 28.6%). Most prostate and ureteral pts either progressed on lurbinectedin or were NE (Prostate: 1 PR, 2 PD, and 2 NE; Ureteral: 1 PD and 1 NE). For all 14 pts, median OS was 11.47 months (95% CI: 2.17-13.63) and median PFS was 2.8 mo (1.4-10.9). Median DoR was 7.38 mo (2.3-9.53) for 4 responding pts (CR or PR). Treatment was stopped due to progression (9/14, 64.3%), three adverse events [thrombocytopenia, electrolyte abnormalities, cerebrovascular accident] (3/14, 21.4%), and pt preference (1/14, 7.1%). Conclusions: Lurbinectedin offers encouraging responses (DCR: 5/7, 71.4%) close to those in SCLC, in previously treated bladder mNEC. One CR was noted for a bladder pt with LCNEC. Responses were less appreciated in prostate and ureteral mNEC due to NE responses and limited number. Larger cohorts are needed to confirm survival benefit and genetic analyses are warranted to identify characteristics of responders. [Table: see text]

572 Background: Bladder preservation with trimodal therapy (TMT), which consists of maximal transurethral resection of bladder tumors followed by chemoradiation, is now included in guidelines with radical cystectomy (RC) as options for definitive management of muscle-invasive bladder cancer (MIBC). Prospective randomized controlled trial data to help guide treatment selection are lacking, and prior efforts to bridge this knowledge gap have failed primarily due to poor accrual. A recent retrospective analysis comparing TMT to RC reported similar oncologic outcomes between these treatments when performed in highly selected patients. However, treatment toxicities and costs vary significantly between these management options. To investigate the impact of these outcomes on relative treatment value, we evaluated the comparative cost-effectiveness of TMT and RC for treatment of MIBC. Methods: Cost-effectiveness was compared between TMT and RC for patients with a solitary, muscle-invasive tumor less than 7cm, no or unilateral hydronephrosis, limited carcinoma in situ, and adequate bladder function (criteria utilized in a recent retrospective comparative series) using a microsimulation model with a 5-year horizon from a Medicare payer perspective. Additionally, a 10-year lifetime horizon was evaluated to better understand the impact of long-term outcome uncertainty on cost-effectiveness. Based on recently published multicenter retrospective propensity score matched data, metastatic progression and survival probabilities were assumed to be equivalent between treatments. Utility values and additional probabilities, including both short and long-term treatment toxicities, were obtained from published literature. Primary outcomes of interest included effectiveness measured in quality adjusted life years (QALYs) and incremental cost-effectiveness ratios (ICER) using a willingness-to-pay threshold of $100,000/QALY. One-way and probabilistic sensitivity analyses were performed to assess the robustness of the model. Results: At 5 years, the average cost was $32,286.35 higher for TMT versus RC. The average QALYs were 3.88 and 3.96 for RC and TMT respectively. TMT was not cost-effective at 5-year (ICER: $379,917.21/QALY) or 10-year (ICER: $222,704.78/QALY) time horizons. On one-way sensitivity analyses, TMT would become cost effective if: 1) TMT costs were less than $16,152; or 2) TMT resulted in a 13.3% improvement in metastasis free survival relative to RC. Conclusions: Although it resulted in similar quality and duration of life, TMT was not cost-effective relative to RC at 5 and 10 years given higher treatment costs. These findings support the role of both TMT and RC in management of MIBC and highlight the need for continued efforts to reduce healthcare costs associated with TMT.