Prediction of response to neoadjuvant chemotherapy of patients with muscle invasive bladder cancer by molecular subtyping and antibody drug conjugate target gene quantitation: Preview of Bladder BRIDGister.
Authors: Wirtz Ralph M. , Voss Paula Carolin , Friedersdorff Frank , Barski Dimitri , Otto Thomas , Waldner Michael , Veltrup Elke , Linden Friederike , Schwandt Meike , Hake Roland , Eidt Sebastian , Roggisch Jenny , Rieger Constantin , Kastner Lucas , Heidenreich Axel , Koch Stefan , Ecke Thorsten H 
Published: March 2023

545 Background: Patients with muscle invasive urothelial carcinoma achieving pathological complete response (pCR) upon neoadjuvant chemotherapy (NACT) have improved prognosis. Molecular subtypes of bladder cancer differ markedly with regard to sensitivity to cisplatinum based chemotherapy. Previously we did show that luminal tumors respond better to NACT, while FGFR1 expression is associated with chemo resistance (Ecke et al. 2022). The objective of this study was to determine which patients may benefit from Antibody Drug Conjugate (ADC) treatment in addition to NACT to justify subsequent prospective analysis within the "Bladder BRIDGister". Methods: Formalin fixed paraffin embedded (FFPE) tissues from transurethral resections (TUR) before chemotherapy and cystectomy samples after NACT of 36 patients were retrospectively collected. RNA from FFPE tissues were extracted by commercial kits, relative gene expression of subtyping markers (KRT5, KRT20, FGFR1) and radioligand target genes (NECTIN4, TROP2) were analyzed by standardized RT-qPCR systems (STRATIFYER Molecular Pathology GmbH, Cologne). Spearman correlation, hierarchical clustering, Kruskal-Wallis, chi square and contingency tests were done by JMP 9.0.0 (SAS software). Results: The neoadjuvant cohort consisted of 36 patients (median age: 69, male 83% vs. female 17%) with 92% of patients being pathohistologically node negative. When comparing pretreatment with post treatment samples the median expression of KRT20 dropped 128fold, while FGFR1 expression increased 6.8 fold. Interestingly, TROP2 and NECTIN4 mRNA expression also dropped significantly upon NACT by 5.7 fold and 7.1 fold, respectively. TROP2 and NECTIN4 were positively associated with the response marker KRT20 in therapy naïve TUR biopsies (r=0.5562 p=0.0004; r=0.5833 p=0.0002), but negatively associated with the resistance marker FGFR1 (r=-0.2903 p=0,0858; r=-0.3396 p=0,0427). However, TROP2 and NECTIN4 were not associated with pCR in spearman analysis with minor trend for TROP2 (r=0,2139 p=0,2103). Cluster analysis revealed a subgroup of KRT20 positive and FGFR1 negative tumors expression TROP2 and NECTIN4, which achieved 80% pCR. In addition elevated TROP2 and NECTIN4 expression was found in KRT20 positive tumors coexpressing FGFR1 and being resistant to NACT. Conclusions: Expression of the ADC targets TROP2 and NECTIN4 is associated with KRT20 positive, luminal tumors being highly sensitive to neoadjuvant chemotherapy alone. KRT5 positive, basal tumors do exhibit only very low expression of TROP2 and NECTIN4 mRNA. In view of toxicities the addition of TROP2 and NECTIN4 treatment to NACT might be considered only in luminal tumors exhibiting elevated FGFR1 expression as resistance mechanism and therefore do not respond to NACT.