Immunohistochemistry-based taxonomical classification of bladder cancer predicts response to neoadjuvant chemotherapy

Abstract

Platinum-based neoadjuvant chemotherapy (NAC) increases the survival of patients with organ-confined urothelial bladder cancer (UBC). Because not all patients benefit from treatment, NAC has not been widely applied in the clinical setting. There is strong evidence, based on retrospective studies, that patients with Basal/Squamous (BASQ)-like tumours present with more advanced disease and have worse prognosis; global transcriptomics can identify tumour subtypes associated with response to NAC. We aimed to investigate whether tumour immunohistochemical (IHC) subtyping predicts NAC response. Patients with muscle-invasive UBC having received platinum-based NAC were identified in two hospitals in Spain. Tissue microarrays were constructed; RNA and DNA were extracted from full sections. Nanostring analysis and immunohistochemistry to identify BASQ-like tumours and mutational analysis of UBC oncogenes. We used hierarchical clustering to classify 126 tumours and adjusted logistic regression to assess association with treatment response. Outcomes were progression-free survival and disease-specific survival; univariable and multivariate Cox regression models were applied. We found very high concordance between mRNA and protein for the 4 markers analyzed. We identified three main subgroups: BASQ-like (FOXA1/GATA3 low; KRT5/6/14 high), Luminal-like (FOXA1/GATA3 high; KRT5/6/14 low), and mixed-cluster (FOXA1/GATA3 high; KRT5/6 high; KRT14 low). Patients with BASQ-like tumours were more likely to achieve a pathological response to NAC, displaying a disease-specific survival similar to that of the remaining patients. In conclusion, patients with BASQ-like tumours - identified through simple and robust immunohistochemistry - have a higher likelihood of undergoing a pathological complete response to NAC. Prospective validation in independent series is required.Novelty and impactNeoadjuvant chemotherapy is an important component of the management of patietns with muscle-invasive bladder cancer but improved stratification is necessary. This retrospective study shows that patients with BASQ-like tumors can be identified using immunohistochemistry on paraffin-embedded tissue and are 4-fold more likely to achieve a pathological complete response to platinum-based NAC. The disease-specific survival of patients with BASQ-like tumours treated with NAC was not different from that of other tumour subtypes.

Association of Immunohistochemical Markers of Tumor Subtype with Response to Neoadjuvant Chemotherapy and Survival in Patients with Muscle-Invasive Bladder Cancer

“…In a retrospective analysis of bladder cancer patients treated with chemoradiation, the impact of IHC-based subtypes on survival and CR to chemoradiation therapy have been assessed by Tanaka et al [19]. More recently, consistent with our experience, Front et al have shown that the patients with basal/squamous (BASQ)-like tumors (KRT5/6/KRT14 high; FOXA1/GATA3 low) were more likely to achieve a CR to NAC (odds ratio, 3.96; p = 0.017) [20]. Compared with our study, similar results were also observed by Front et al regarding the subtype-related survival outcomes.…”

Immunohistochemical assays for bladder cancer molecular subtyping: Optimizing parsimony and performance using Lund taxonomy

“…Notably, much of the current literature highlights the utility of the same key differentiation markers described in these models and ROC analysis as candidate assays for subtype identification (10,(17)(18)(19)(20). A number of studies propose a combination of two to four luminal and basal protein features such as FOXA1, GATA3, KRT5/6 and KRT14 (10,19,20) for bladder cancer subtyping.…”

“…Work from the Lund group has identified further prognostic differences amongst the luminal subtypes, such that the GU subtype experiences a worse prognosis relative to its Uro counterpart. Molecular subtypes have also been associated with response to neoadjuvant chemotherapy and immune checkpoint blockade (3,(8)(9)(10)(11)(12)(13). These predictive and prognostic associations indicate potential clinical applications of subtyping.…”

“…Indeed, recent work has focused on using IHC to identify luminal and basal subtypes (10,(18)(19)(20). Multiple studies identified key immunohistochemical protein features capable of achieving high accuracy for identifying mRNA-subtypes (10,(18)(19)(20). However, to our knowledge this work has yet to extend beyond luminal/basal subtyping and has focused on validating mRNA subtypes as opposed to the tumor cell phenotypes (IHC subtypes) clarified by the Lund taxonomy.…”

“…Given its simplicity and availability in routine clinical pathology labs, IHC may serve as an attractive, simple alternative to transcriptomic profiling. Indeed, recent work has focused on using IHC to identify luminal and basal subtypes (10,(18)(19)(20). Multiple studies identified key immunohistochemical protein features capable of achieving high accuracy for identifying mRNA-subtypes (10,(18)(19)(20).…”