Targeting Circulating Tumor Cells in Pancreatic Ductal Adenocarcinoma: Rationale, Current Evidence, and a CEACAM6 CAR-T Strategy

Background: Pancreatic ductal adenocarcinoma (PDAC) exhibits high post-resection relapse and early systemic dissemination rates. The level of circulating tumor cells (CTCs) correlates with early metastatic failure, motivating CTC interception strategies. Methods: In this hypothesis-driven review, we synthesized the contemporary evidence on PDAC staging and therapy, CTC detection (including portal versus peripheral sampling), and circulating tumor DNA (ctDNA)-based minimal residual disease (MRD), and evaluated the translational rationale for CTC-targeted adoptive immunotherapy focusing on CEACAM6 and CAR-T cells. Results: Prospective studies report higher portal versus peripheral CTC yields and stronger associations with relapse; tumor-informed ctDNA positivity in peri-operative and surveillance windows predicts shorter disease-free survival. CEACAM6 is overexpressed in PDAC and linked to invasion and metastasis, supporting antigen selection. However, target overexpression alone does not establish clinical suitability for adoptive cell transfer. Consequently, its therapeutic implementation must contend with assay heterogeneity, on-target/off-tumor risks, and the lack of interventional outcome data in PDAC, all of which remain key hurdles. Conclusions: CTC-targeting is biologically plausible and operationally measurable in PDAC. Consequently, a CEACAM6-directed CAR-T approach is proposed as a potential strategy for the interception of minimal residual disease (MRD). Randomized and biomarker-selected trials with composite MRD-clearance endpoints (CTC < LOQ and ctDNA-negative) may be justified to validate this interventional hypothesis.