Transcriptomic FOLFIRINOX sensitivity signatures stratify overall survival and reveal directional reclassification after neoadjuvant FOLFIRINOX in borderline resectable and locally advanced pancreatic cancer

Background: Transcriptomic FOLFIRINOX-component sensitivity signatures have been clinically evaluated in resected and advanced PDAC, but their relevance and longitudinal stability in the neoadjuvant BR/LA setting are unknown. Patients and methods: We retrospectively studied 77 patients with borderline resectable or locally advanced PDAC treated with neoadjuvant FOLFIRINOX followed by resection. Pretreatment sensitivity to 5-fluorouracil, oxaliplatin and irinotecan was determined using previously developed locked transcriptomic classifiers and integrated into a regimen-level FOLFIRINOX classification. The primary molecular cohort comprised 53 patients whose pretreatment biopsies had [≥]10% tumour cellularity. Cox models assessed associations with survival. Longitudinal changes were assessed in 35 paired tumours. Results: Thirty-one pretreatment tumours were classified as FOLFIRINOX-sensitive (FFX-Sens), and 22 were not classified as FOLFIRINOX-sensitive (FFX-Res). FFX-Sens status was associated with longer overall survival (OS; hazard ratio [HR] 0.48, 95% confidence interval [CI] 0.25-0.93; p=0.029). In the complete-case model adjusted for baseline carbohydrate antigen 19-9 (CA19-9) and tumour size (n=50), the association with OS persisted (adjusted HR 0.47, 95% CI 0.23-0.96; p=0.037), whereas the adjusted association with disease-free survival was not statistically significant (adjusted HR 0.55, 95% CI 0.28-1.10; p=0.090). Among paired tumours, 15 changed from FFX-Sens to FFX-Res and four in the opposite direction (exact McNemar p=0.019). The OS association also persisted after adjustment for postoperative pathological factors (adjusted HR 0.40; p=0.015). Conclusions: Pretreatment FOLFIRINOX sensitivity was associated with OS under neoadjuvant FOLFIRINOX, while matched pretreatment and residual-tumour analyses revealed significant directional reclassification after treatment. These findings extend the clinical evaluation of validated drug-specific FOLFIRINOX sensitivity classifiers to the neoadjuvant setting and provide a longitudinal assessment of their stability during treatment. They support prospective evaluation of both pretreatment stratification and molecular reassessment of residual disease.