Abstract
The Coexpression Extrapolation (COXEN) gene expression model with chemotherapy-specific scores [for methotrexate, vinblastine, adriamycin, cisplatin (ddMVAC) and gemcitabine/cisplatin (GC)] was developed to identify responders to neoadjuvant chemotherapy (NAC). We investigated RNA-based molecular subtypes as additional predictive biomarkers for NAC response, progression-free survival (PFS), and overall survival (OS) in patients treated in S1314.
A total of 237 patients were randomized between four cycles of ddMVAC (51%) and GC (49%). On the basis of Affymetrix transcriptomic data, we determined subtypes using three classifiers: TCGA (k = 5), Consensus (k = 6), and MD Anderson (MDA; k = 3) and assessed subtype association with path response to NAC and determined associations with COXEN. We also tested whether each classifier contributed additional predictive power when added to a model based on predefined stratification (strat) factors (PS 0 vs. 1; T2 vs. T3, T4a).
A total of 155 patients had gene expression results, received at least three of four cycles of NAC, and had pT-N response based on radical cystectomy. TCGA three-group classifier basal-squamous (BS)/neuronal, luminal (Lum), Lum infiltrated, and GC COXEN score yielded the largest AUCs for pT0 (0.59, P = 0.28; 0.60, P = 0.18, respectively). For downstaging (<pT2), the three-category Consensus classifier [BS/neuroendocrine (NE)-like, Lum, stroma-rich] increased the AUC from 0.57 (strat factors alone) to 0.61 (P = 0.10). The MDA classifier AUC was 0.63 (P = 0.18) and the GC COXEN score AUC was 0.62 (P = 0.23), but neither significantly improved the AUC. There was no statistically significant association of stratification factors and subtypes with PFS or OS.
The Consensus classifier, based in part on the TCGA and MDA classifiers, modestly improved prediction for pathologic downstaging but subtypes were not associated with PFS or OS.
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