Predicting prognosis and optimal timing for surgery using CA 19-9 in patients with pancreatic cancer who underwent FOLFIRINOX-based neoadjuvant therapy: a retrospective single-center cohort study.

Purpose: Neoadjuvant therapy (NAT) followed by surgical resection is the standard treatment for borderline resectable pancreatic cancer. The optimal timing for surgery after NAT, however, is unclear. Methods: This study retrospectively analyzed 83 patients who underwent NAT followed by resection between January 2018 and December 2021. Results: Before NAT, 22.9% of patients had resectable disease, 57.8% had borderline resectable disease, and 19.3% had locally advanced disease. After NAT, 26.5% of patients showed a downstaging of their clinical stage. After NAT, median CA 19-9 levels decreased from 148.0 to 31.7, mean tumor size from 3.1 to 2.3 cm, and the mean PET-CT maximum standardized uptake value from 6.3 to 3.6. Three-year overall survival (OS) and recurrence-free survival (RFS) were 46.7% and 22.6%, respectively. RFS and OS were significantly associated with CA 19-9 levels, lymph node metastasis, and postsurgical pathological stage, while OS was also significantly associated with tumor size and NAT. Patients with elevated CA 19-9 (> 37) which normalized after NAT showed a 3-year RFS of 32.5% compared to 0.0% in those who did not. In patients with elevated CA 19-9, OSs were 58.3% and 25.0% for those with a post-NAT decrease of ≥70% vs. those with no decrease, respectively, while RFSs were 22.6% and 0%. Conclusion: Timing of surgery after NAT should be decided considering post-NAT tumor size and CA 19-9 levels.