Genomic Biomarkers for First-Line Treatment Selection in Metastatic Pancreatic Ductal Adenocarcinoma: A Narrative Review.

Metastatic pancreatic ductal adenocarcinoma (PDAC) is typically treated with fluorouracil, leucovorin, irinotecan, and oxaliplatin (FOLFIRINOX) or gemcitabine plus nab-paclitaxel (GnP), but the choice between regimens remains largely empirical. This narrative review summarizes biomarkers with potential to inform first-line selection in metastatic PDAC, emphasizing genomic and transcriptomic correlates of differential benefit. Recent head-to-head trials, particularly Pancreatic Adenocarcinoma Signature Stratification for Treatment (PASS-01) and GENERATE (Japan Clinical Oncology Group [JCOG] 1611), indicate that modified FOLFIRINOX (mFOLFIRINOX) is not uniformly superior to GnP, strengthening the rationale for biomarker-guided selection. The strongest evidence favoring platinum-based/FOLFIRINOX strategies involves homologous recombination repair deficiency (HRD), especially alterations in germline breast cancer gene 1/2 (BRCA1/2) or partner and localizer of BRCA2 (PALB2), as well as broader genomic scar signatures. Transcriptomic subtype and GATA-binding protein 6 (GATA6) expression are promising but remain unsettled because retrospective data favor classical/GATA6-high disease for FOLFIRINOX, whereas PASS-01 suggested better outcomes with GnP in classical tumors. Candidate biomarkers favoring GnP include high human equilibrative nucleoside transporter 1 (hENT1), low class III β-tubulin (TUBB3) expression, and exploratory phosphatidylinositol 3-kinase (PI3K)/KIT/NOTCH pathway mutation signals. Comprehensive molecular profiling also identifies actionable alterations that may redirect patients to targeted therapy or clinical trials rather than standard chemotherapy alone. Importantly, no biomarker has yet been prospectively validated in a biomarker-stratified randomized trial with regimen selection as the primary endpoint; all biomarker-regimen associations described in this review should therefore be considered hypothesis-generating rather than practice-defining. Nevertheless, the convergence of genomic, transcriptomic, and organoid-based approaches makes biologically informed first-line selection increasingly feasible in metastatic PDAC.