Clinicopathological characteristics and loss of mismatch repair protein expression in Chinese upper tract urothelial carcinomas

Assessment of the Prognostic and Predictive Values of the Deficient Mismatch Repair Phenotype in Patients Treated with Radical Nephroureterectomy for Upper Tract Urothelial Carcinoma

BACKGROUND AND OBJECTIVE

Given the conflicting evidence currently available in the literature, our aim was to assess the prognostic and predictive values of the deficient mismatch repair (dMMR) phenotype in a large cohort of upper tract urothelial carcinoma (UTUC) patients.

METHODS

Based on our national network, we performed a retrospective multicenter study including 281 UTUC patients treated with radical nephroureterectomy between 2000 and 2015 at ten French hospitals. The dMMR phenotype as well as PD-L1 and PD-1 expression were determined using immunohistochemistry analyses based on 2-mm-core tissue microarrays. Multivariable Cox regression models were fitted to assess the impact of the dMMR phenotype on recurrence-free (RFS), cancer-specific (CSS), and overall (OS) survival using interaction terms to test the heterogeneity of the treatment effect of adjuvant chemotherapy (AC). Multivariable logistic regression models were also fitted to assess the impact of the dMMR phenotype on PD-L1 and PD-1 expression.

KEY FINDINGS AND LIMITATIONS

Overall, 76 (27.0%) patients had a dMMR phenotype, which was an independent predictor of prolonged RFS (hazard ratio [HR] = 0.41; 95% confidence interval [CI] = [0.21-0.83]; p = 0.01), CSS (HR = 0.38; 95% CI = [0.18-0.83]; p = 0.02), and OS (HR = 0.44; 95% CI = [0.22-0.89]; p = 0.02), with a significant interaction with the use of AC in multivariable Cox regression models (all pinteraction < 0.05). Subgroup analyses showed that the use of AC was significantly associated with prolonged RFS (HR = 0.14; 95% CI = [0.06-0.30]; p < 0.001), CSS (HR = 0.10; 95% CI = [0.03-0.29]; p < 0.001), and OS (HR = 0.23; 95% CI = [0.10-0.54]; p = 0.001) in non-dMMR patients only, without any significant benefit in dMMR patients (all p > 0.05). In multivariable logistic regression analyses, the dMMR phenotype was significantly associated with inverse PD-L1 (OR = 0.20; 95% CI = [0.10-0.80]; p = 0.001) and PD-1 (OR = 0.36; 95% CI = [0.16-0.79]; p = 0.01) expression.

CONCLUSIONS AND CLINICAL IMPLICATIONS

We observed that the dMMR phenotype was associated with favorable pathological characteristics and prognosis in UTUC patients, despite conferring decreased sensitivity to AC and lower PD-L1 or PD-1 expression.

A collaborative review of the microsatellite instability/deficient mismatch repair phenotype in patients with upper tract urothelial carcinoma

OBJECTIVE

To perform a collaborative review of the literature exploring the microsatellite instability/deficient mismatch repair (MSI/dMMR) phenotype in patients with upper tract urothelial carcinoma (UTUC).

METHOD

A collaborative review of the literature available on Medline was conducted by the Cancer Committee of the French Association of Urology to report studies describing the genetic mechanisms, investigation, prevalence and impact of the MSI/dMMR phenotype in UTUC patients.

RESULTS

The predominant genetic mechanism leading to the MSI/dMMR phenotype in UTUC patients is related to the constitutional mutation of one allele of the MMR genes MLH1, MSH2, MSH6 and PMS2 within Lynch syndrome. Indications for its investigation currently remain limited to patients with a clinical suspicion for sporadic UTUC to refer only those with a positive testing for germline DNA sequencing to screen for this syndrome. With regard to technical aspects, despite the interest of MSIsensor, only PCR and immunohistochemistry are routinely used to somatically investigate the MSI and dMMR phenotypes, respectively. The prevalence of the MSI/dMMR phenotype in UTUC patients ranges from 1.7% to 57%, depending on the study population, investigation method and definition of a positive test. Younger age and a more balanced male to female ratio at initial diagnosis are the main specific clinical characteristics of UTUC patients with an MSI/dMMR phenotype. Despite the conflicting results available in the literature, these patients may have a better prognosis, potentially related to more favourable pathological features. Finally, they may also have lower sensitivity to chemotherapy but greater sensitivity to immunotherapy.

CONCLUSION

Our collaborative review summarises the available data from published studies exploring the MSI/dMMR phenotype in UTUC patients, the majority of which are limited by a low level of evidence.

Clinicopathological characteristics, molecular landscape, and biomarker landscape for predicting the efficacy of PD-1/PD-L1 inhibitors in Chinese population with mismatch repair deficient urothelial carcinoma: a real-world study

Urothelial carcinoma (UC) with deficient mismatch repair (dMMR) is a specific subtype of UC characterized by the loss of mismatch repair (MMR) proteins and its association with Lynch syndrome (LS). However, comprehensive real-world data on the incidence, clinicopathological characteristics, molecular landscape, and biomarker landscape for predicting the efficacy of PD-1/PD-L1 inhibitors in the Chinese patients with dMMR UC remains unknown. We analyzed 374 patients with bladder urothelial carcinoma (BUC) and 232 patients with upper tract urothelial carcinoma (UTUC) using tissue microarrays, immunohistochemistry, and targeted next-generation sequencing. Results showed the incidence of dMMR UC was higher in the upper urinary tract than in the bladder. Genomic analysis identified frequent mutations in KMT2D and KMT2C genes and LS was confirmed in 53.8% of dMMR UC cases. dMMR UC cases displayed microsatellite instability-high (MSI-H) (PCR method) in 91.7% and tumor mutational burden-high (TMB-H) in 40% of cases. The density of intratumoral CD8+ T cells correlated with better overall survival in dMMR UC patients. Positive PD-L1 expression was found in 20% cases, but some patients positively responded to immunotherapy despite negative PD-L1 expression. Our findings provide valuable insights into the characteristics of dMMR UC in the Chinese population and highlights the relevance of genetic testing and immunotherapy biomarkers for treatment decisions.