Tumor Mutational Burden as a Predictor of First-Line Immune Checkpoint Inhibitor Versus Carboplatin Benefit in Cisplatin-Unfit Patients With Urothelial Carcinoma

Molecular Classification of Urothelial Carcinoma

Urothelial carcinoma exhibits a wide spectrum of morphologic and molecular heterogeneity. Advances in molecular testing have improved our understanding of the molecular biology of urothelial carcinoma, including recurrent genomic alterations and transcriptomic features, leading to the development of molecular classification schemes with potential therapeutic implications. This review summarizes the molecular characteristics of urothelial carcinoma, focusing on genomic and transcriptomic features, updates on variant histology, and novel biomarkers that may guide contemporary and future clinical management.

Tumor mutational burden and survival on immune checkpoint inhibition in >8000 patients across 24 cancer types

BACKGROUND

There is uncertainty around clinical applicability of tumor mutational burden (TMB) across cancer types, in part because of inconsistency between TMB measurements from different platforms. The KEYNOTE 158 trial supported United States Food and Drug Administration (FDA) approval of the Foundation Medicine test (FoundationOneCDx) at TMB≥10 mut/Mb as a companion diagnostic (CDx) for single-agent pembrolizumab in second+line. Using a large real-world dataset with validated survival endpoint data, we evaluated clinical validity of TMB measurement by the test in over 8000 patients across 24 cancer types who received single-agent immune checkpoint inhibitor (ICI).

METHODS

Patients with advanced-stage cancers from 24 cancer types treated with single-agent anti-PD(L)1 therapy in standard-of-care settings were included. Deidentified data from electronic health records from approximately 280 cancer treatment facilities were captured into a clinico-genomic database. This study used the TMB algorithm from the FDA-approved test supporting solid tumor CDx and composite mortality variable validated against the national death index: real-world overall survival (rwOS). Following a prespecified analysis plan, rwOS by TMB level was assessed using Cox PH models adjusted for Eastern Cooperative Oncology Group performance status, prior treatment, microsatellite instability, sex, age, opioid rx pretherapy, and socioeconomic assessment.

RESULTS

8440 patients met inclusion criteria. Adjusting for aforementioned factors, increasing TMB was significantly associated with rwOS across tumor types; HRs (95% CIs) relative to TMB<5: TMB 5 to <10: 0.95 (0.89 to 1.02), TMB 10 to <20: 0.79 (0.73 to 0.85), TMB≥20: 0.52 (0.47 to 0.58). For individual cancer types with prespecified statistical power, adjusted rwOS comparing TMB≥10 vs TMB<10 significantly favored TMB≥10 in 9 of 10 cancer types. In microsatellite stable subcohorts (except colorectal cancer), TMB≥10 remained associated with enriched ICI benefit. Exploratory assessments of patients receiving ICI+chemotherapy (n=4369) observed more favorable rwOS only in TMB≥20.

CONCLUSIONS

Across >8000 patients treated with single-agent ICI, and within individual cancer types with sufficient power, elevated TMB based on the FDA-approved CDx was associated with more favorable rwOS compared with similar patients with lower TMB levels. This biomarker deserves further clinical investigation to potentially guide the use of immunotherapy in expanded clinical contexts.

Tumor mutational burden: why is it still a controversial agnostic immunotherapy biomarker?

For the past few years, researchers and oncologists have been pushing to find biomarkers that would help predict which treatment option would best work on a patient. Tumor Mutational Burden (TMB) is one of the latest biomarkers that is being studied and considered as a promising agnostic immunotherapy biomarker. However, it still shows controversial results in studies due to the difficulty in finding solid comparable results. This is a consequence of different cutoff definitions among many cancer types, age ranges, and the use of different sequencing assays, in addition to its association with other biomarkers such as PD-L1. Finally, the use of composite biomarkers to assess the genetic signature of a tumor might be the way forward to seriously use TMB as an agnostic biomarker.

Association of Tumor Mutational Burden and PD-L1 with the Efficacy of Pembrolizumab with or without Chemotherapy versus Chemotherapy in Advanced Urothelial Carcinoma

PURPOSE

The three-arm, phase III KEYNOTE-361 study did not meet its dual primary endpoints of progression-free survival (PFS) or overall survival (OS) with first-line pembrolizumab plus chemotherapy versus chemotherapy in advanced urothelial carcinoma. This prespecified exploratory analysis assessed the association of tumor mutational burden (TMB) and PD-L1 combined positive score (CPS) with clinical outcomes.

PATIENTS AND METHODS

TMB and PD-L1 CPS were determined via whole-exome sequencing and PD-L1 IHC 22C3 pharmDx, respectively. The association was evaluated in each treatment arm using logistic regression [objective response rate (ORR)] and Cox proportional hazards regression models (PFS and OS); one-sided (pembrolizumab monotherapy; pembrolizumab plus chemotherapy) and two-sided (chemotherapy) nominal P values were calculated. Significance was prespecified at α = 0.05 without multiplicity adjustment. Efficacy was evaluated by prespecified cutoffs of 175 mutations/exome (TMB) and CPS 10 (PD-L1).

RESULTS

Of the 993 treated patients, 820 (82.6%) and 993 (100%) had evaluable TMB and CPS data, respectively. Continuous TMB was positively associated with ORR, PFS, and OS for pembrolizumab monotherapy (one-sided P < 0.001, P < 0.001, and P = 0.007, respectively); PFS and OS for pembrolizumab plus chemotherapy (one-sided P = 0.007 and P = 0.010, respectively); and OS for chemotherapy alone (two-sided P = 0.040). Continuous PD-L1 CPS showed evidence of anticipated association with ORR and PFS for pembrolizumab monotherapy. The subgroup with TMB ≥175 mutations/exome and PD-L1 CPS ≥10 had the highest PFS and OS improvements with pembrolizumab alone or with chemotherapy versus chemotherapy alone.

CONCLUSIONS

These data suggest that TMB may be predictive of the response to pembrolizumab alone or with chemotherapy in advanced urothelial carcinoma.

How Immunotherapy Has Redefined the Treatment Paradigm of Metastatic or Locally Advanced Muscle-Invasive Urothelial Bladder Carcinoma

In the past decade, the therapeutic arsenal for metastatic bladder cancer has expanded considerably, with the development of immune checkpoint inhibitors (ICIs), antibody-drug conjugates such as enfortumab vedotin, and anti-fibroblast growth factor receptor agents. Clinical trials evaluating ICIs as neoadjuvants, adjuvants, or first- or second-line treatments have produced conflicting results. However, first-line therapeutic strategies have been redefined by the recent publication of results from two clinical trials: CheckMate-901, which demonstrated the superiority of combined treatment with nivolumab and chemotherapy in extending overall survival, and EV-302, which demonstrated that combined treatment with pembrolizumab and enfortumab vedotin reduced the risk of death by 53%. In this review, we discuss the role of ICIs, alone or in combination, in bladder cancer management in the metastatic and adjuvant settings in 2024, considering the latest published trials. The potential role of ICIs as neoadjuvants is also discussed.

RAS/RAF Comutation and ERBB2 Copy Number Modulates HER2 Heterogeneity and Responsiveness to HER2-directed Therapy in Colorectal Cancer

PURPOSE

ERBB2-amplified colorectal cancer is a distinct molecular subtype with expanding treatments. Implications of concurrent oncogenic RAS/RAF alterations are not known.

EXPERIMENTAL DESIGN

Dana-Farber and Foundation Medicine Inc. Colorectal cancer cohorts with genomic profiling were used to identify ERBB2-amplified cases [Dana-Farber, n = 47/2,729 (1.7%); FMI, n = 1857/49,839 (3.7%)]. Outcomes of patients receiving HER2-directed therapies are reported (Dana-Farber, n = 9; Flatiron Health-Foundation Medicine clinicogenomic database, FH-FMI CGDB, n = 38). Multisite HER2 IHC and genomic profiling were performed to understand HER2 intratumoral and interlesional heterogeneity. The impact of concurrent RAS comutations on the effectiveness of HER2-directed therapies were studied in isogenic colorectal cancer cell lines and xenografts.

RESULTS

ERBB2 amplifications are enriched in left-sided colorectal cancer. Twenty percent of ERBB2-amplified colorectal cancers have co-occurring oncogenic RAS/RAF alterations. While RAS/RAF WT colorectal cancers typically have clonal ERBB2 amplification, colorectal cancers with co-occurring RAS/RAF alterations have lower level ERRB2 amplification, higher intratumoral heterogeneity, and interlesional ERBB2 discordance. These distinct genomic patterns lead to differential responsiveness and patterns of resistance to HER2-directed therapy. ERBB2-amplified colorectal cancer with RAS/RAF alterations are resistant to trastuzumab-based combinations, such as trastuzumab/tucatinib, but retain sensitivity to trastuzumab deruxtecan in in vitro and murine models. Trastuzumab deruxtecan shows clinical efficacy in cases with high-level ERBB2-amplified RAS/RAF coaltered colorectal cancer.

CONCLUSIONS

Co-occurring RAS/RAF alterations define a unique subtype of ERBB2-amplified colorectal cancer that has increased intratumoral heterogeneity, interlesional discordance, and resistance to trastuzumab-based combinations. Further examination of trastuzumab deruxtecan in this previously understudied cohort of ERBB2-amplified colorectal cancer is warranted.

Real world evidence of enfortumab vedotin in patients with advanced urothelial cancer: A multicenter observational study

OBJECTIVES

To explore the characteristics of patients and assess the effectiveness of enfortumab vedotin (EV) in those with treatment-resistant advanced urothelial cancer in a real-world setting.

PATIENTS AND METHODS

A multicenter observational study was conducted on 103 evaluable patients with advanced urothelial cancer who received EV. Outcomes were assessed by radiographic response, progression-free survival (PFS), and overall survival (OS), with treatment-related adverse events (trAEs). Radiographic response was assessed using Response Evaluation Criteria in Solid Tumors version 1.1, while trAEs were studied in line with Common Terminology Criteria for Adverse Events version 5.0.

RESULTS

The median follow-up was 8.9 months (range, 0.1-16.4). The observed objective response rate was 50.5%. The median PFS was 6.0 months (95% CI: 4.7-9.8), and the median OS was 14.5 months (95% CI: 12.4-not reached). Out of the 103 patients, 19 (18.4%) had an Eastern Cooperative Oncology Group performance status of 2 or more, 14 (14.7%) had an non-urothelial carcinoma histology, and 40 (38.3%) had at least one pre-existing comorbidity. There were 26 (25.2%) patients who reported 49 trAEs, with 9 (18.3%) being grade 3 or higher. The most common trAEs included rash, occurring in 18.4%.

CONCLUSIONS

This study describes the characteristics and outcomes of patients with previously treated advanced urothelial cancer receiving EV. The findings demonstrate that EV showed robust anti-tumor activity and had manageable safety profiles outside the clinical trial setting.

Current and Emerging Strategies to Treat Urothelial Carcinoma

Urothelial cell carcinoma (UCC, bladder cancer, BC) remains a difficult-to-treat malignancy with a rising incidence worldwide. In the U.S., UCC is the sixth most incident neoplasm and ~90% of diagnoses are made in those >55 years of age; it is ~four times more commonly observed in men than women. The most important risk factor for developing BC is tobacco smoking, which accounts for ~50% of cases, followed by occupational exposure to aromatic amines and ionizing radiation. The standard of care for advanced UCC includes platinum-based chemotherapy and programmed cell death (PD-1) or programmed cell death ligand 1 (PD-L1) inhibitors, administered as frontline, second-line, or maintenance therapy. UCC remains generally incurable and is associated with intrinsic and acquired drug and immune resistance. UCC is lethal in the metastatic state and characterized by genomic instability, high PD-L1 expression, DNA damage-response mutations, and a high tumor mutational burden. Although immune checkpoint inhibitors (ICIs) achieve long-term durable responses in other cancers, their ability to achieve similar results with metastatic UCC (mUCC) is not as well-defined. Here, we discuss therapies to improve UCC management and how comprehensive tumor profiling can identify actionable biomarkers and eventually fulfill the promise of precision medicine for UCC patients.

Tumor Mutational Burden in Real-World Patients With Pancreatic Cancer: Genomic Alterations and Predictive Value for Immune Checkpoint Inhibitor Effectiveness

PURPOSE

Pancreatic ductal adenocarcinoma (PDAC) is largely considered a nonimmunogenic malignancy; however, approximately 1%, of patients may have tumors with deficient mismatch repair, high microsatellite instability, or high tumor mutational burden (TMB ≥10 mutations/Mb), which may be predictive of response to immune checkpoint inhibitor (ICI) therapy. We sought to analyze outcomes of patients with high-TMB and pathogenic genomic alterations observed in this population.

METHODS

This study included patients with PDAC who underwent comprehensive genomic profiling (CGP) at Foundation Medicine (Cambridge, MA). Clinical data were obtained from a US-wide real-world clinicogenomic pancreatic database. We report genomic alterations in those with high and low TMB, and compare outcomes on the basis of receipt of single-agent ICI or therapy regimens not containing ICI.

RESULTS

We evaluated 21,932 patients with PDAC who had tissue CGP data available, including 21,639 (98.7%) with low-TMB and 293 (1.3%) with high-TMB. Among patients with high-TMB, a greater number of alterations were observed in BRCA2, BRAF, PALB2, and genes of the mismatch repair pathway, whereas fewer alterations were observed in KRAS. Among patients who received an ICI (n = 51), those with high-TMB had more favorable median overall survival when compared with the low-TMB subset (25.7 v 5.2 months; hazard ratio, 0.32; 95% CI, 0.11 to 0.91; P = .034).

CONCLUSION

Longer survival was observed in patients with high-TMB receiving ICI compared with those with low-TMB. This supports the role of high-TMB as a predictive biomarker for efficacy of ICI therapy in PDAC. Additionally, we report higher rates of BRAF and BRCA2 mutations and lower rates of KRAS mutation among patients with PDAC and high-TMB, which to our knowledge, is a novel finding.

Neoadjuvant Pembrolizumab and Radical Cystectomy in Patients with Muscle-Invasive Urothelial Bladder Cancer: 3-Year Median Follow-Up Update of PURE-01 Trial

PURPOSE

The PURE-01 study (NCT02736266) pioneered the neoadjuvant immune-checkpoint inhibitor (ICI) therapy before radical cystectomy (RC) in patients with muscle-invasive urothelial bladder carcinoma (MIBC). We herein present the survival outcomes after a median follow-up of three years.

PATIENTS AND METHODS

The intention-to-treat (ITT) population included 155 patients. Event-free survival (EFS) was defined as the time from pembrolizumab initiation until radiographic disease progression precluding RC, initiation of neoadjuvant chemotherapy, recurrence after RC, or death. Further outcomes were recurrence-free survival (RFS) post-RC and overall survival (OS). Multivariable Cox regression analyses for EFS were performed. Kaplan-Meier analyses compared EFS outcomes according with baseline programmed cell-death-ligand-1 (PD-L1) combined positive score (CPS) and according to the molecular subtypes.

RESULTS

After a median (interquartile range, IQR) follow-up of 39 (30-47) months, 36-month EFS and OS were 74.4% [95% confidence interval (CI), 67.8-81.7] and 83.8% (95% CI, 77.8-90.2) in the ITT population, respectively. Overall, 143 (92.3%) patients underwent RC. Within the cohort of patients who did not receive additional chemotherapy (N = 125), 36-month RFS was 96.3% (95% CI, 91.6-100) for patients achieving a ypT0N0, 96.1% (95% CI, 89-100) for ypT1/a/isN0, 74.9% (95% CI, 60.2-93) for ypT2-4N0, and 58.3% (95% CI, 36.2-94.1) for ypTanyN1-3 response. EFS was significantly stratified among PD-L1 tertiles (lower tertile: 59.7% vs. medium tertile: 76.7% vs. higher tertile: 89.8%, P = 0.0013). The claudin-low and basal/squamous subtypes displayed the lowest rates of events.

CONCLUSIONS

At a median follow-up of three years, PURE-01 results further confirm the sustained efficacy of neoadjuvant pembrolizumab before RC. PD-L1 expression was the strongest predictor of sustained response post-RC.

Immunotherapy for Urothelial Carcinoma: Focus on Clinical Utility of Nivolumab

Over the past decade, the emergence of immune checkpoint inhibitors has brought about significant change to the treatment landscape of bladder cancer. Nivolumab is an immune checkpoint inhibitor that has shown favorable results resulting in FDA approval for treatment of platinum-refractory locally advanced or metastatic urothelial carcinoma. More recently, it was the first (and only) immune checkpoint inhibitor to receive FDA approval for the treatment of urothelial carcinoma in the adjuvant setting after radical surgery. Multiple trials are now actively underway to further understand the nuances in which immune checkpoint inhibitors such as nivolumab can be beneficial. In this review, we explore the development of nivolumab in terms of its mechanism of action, its growing indications in the treatment of urothelial carcinoma, and potential future directions for clinical trials. Immune checkpoint inhibitors are a promising treatment for bladder cancer, but further work is needed to continue to improve outcomes for patients.