The 30% reduction of baseline CA19-9 could stratify the prognosis of advanced pancreatic ductal adenocarcinoma with RECIST stable disease after first-line chemotherapy

BACKGROUND: Radiological assessment based on RECIST criteria has limited accuracy in evaluating chemotherapy response in advanced pancreatic ductal adenocarcinoma (PDAC), particularly in patients classified as stable disease. Additional clinically accessible biomarkers are needed to better stratify treatment response and prognosis in this population. METHODS: This study retrospectively included patients with advanced PDAC who received first-line chemotherapy and completed an 8-week response assessment. Contrast-enhanced CT and serum CA19-9 were evaluated every 8 weeks for disease surveillance. The primary endpoints were progression-free survival (PFS) and overall survival (OS). RESULTS: Of 182 patients included, 117 (64.3%), 21 (11.5%), and 44 (24.2%) patients were classified into SD, partial response (PR), and progressive disease (PD) at the first radiological evaluation. The SD cohorts presented OS similar to the PR cohort (P = 0.348). In SD patients with elevated baseline CA19-9 levels, the cohort with a 30% reduction of baseline CA19-9 levels was defined as the CA19-9 response group. Compared with the nonresponse group (decreased < 30% or increased CA19-9 cohorts), the response group presented significantly better PFS (P < 0.001) and OS (P = 0.010). CONCLUSIONS: After 8 weeks of first-line chemotherapy, most patients with advanced PDAC were classified as SD and exhibited survival outcomes comparable to those with partial response. In patients with stable disease and elevated baseline CA19-9 levels, a ≥ 30% reduction in CA19-9 provided additional prognostic stratification.