Transitional Type Circulating Tumor Cells Predict Systemic Recurrence and Support Risk Stratification for Chemotherapy After Resection of Pancreatic Ductal Adenocarcinoma

Aim: To evaluate whether transitional circulating tumor cells (trCTCs) predict systemic recurrence of pancreatic ductal adenocarcinoma (PDAC) and assess their potential role in risk stratification for systemic treatment. Background: The high metastatic potential of PDAC is believed to be associated with early dissemination after cancer cell reprogramming via an epithelial-to-mesenchymal transition. These cells are detectable in circulation as trCTCs and could serve as valuable biomarker capturing systemic disease involvement. Methods: The prospective CLUSTER trial enrolled patients scheduled for PDAC resection (2016–2018). Pre- and postoperative CTCs were isolated with the Isolation-by-SizE-of-Tumor-Cells device and characterized by immunofluorescence. Cox regression with spline terms assessed associations between preoperative biomarkers and systemic recurrence, while multivariable subgroup analyses with interaction tests evaluated overall survival (OS) stratified by adjuvant chemotherapy. Results: In preoperative samples, trCTCs were detected in 82 (67%) of 123 patients with a median number of two cells per ml (IQR 1-3). A linear association between preoperative trCTC counts and systemic recurrence (χ²=13.2, P =0.004) was observed, but no relevant correlation with CA19-9 levels was found (Pearson correlation=0.05, 95% CI:–0.13-0.23). Furthermore, trCTC-positivity after resection predicts recurrence and is associated with prolonged OS associated with adjuvant therapy (HR 0.21, 95%CI: 0.09-0.49) after adjustment for tumor stage and neoadjuvant chemotherapy. Conclusions: Preoperatively, higher trCTC counts are associated with increased risk of systemic recurrence, while postoperative presence reflects minimal residual disease. Integrating trCTC assessment alongside currently used biomarkers into the clinical pathway for patients with PDAC could enhance risk stratification and support more personalized treatment decisions.