Impact of Ca19-9 reduction on resectability and survival in pancreatic cancer patients following neoadjuvant or conversion chemotherapy.

Abstract

765 Background: Surgical curability in pancreatic cancer remains very limited. It is still unclear how this may change following chemotherapy aimed at increasing resectability rates. The objective of this study was to evaluate the impact of Ca19-9 reduction on resectability and overall survival (OS) in patients with pancreatic cancer treated with neoadjuvant or conversion chemotherapy. Methods: We retrospectively analyzed 84 patients with histologically confirmed pancreatic cancer treated with FOLFIRINOX between January 2012 and December 2024 at Instituto do Câncer do Estado de São Paulo (ICESP). Disease status at baseline included 39 borderline resectable (BR), 38 locally advanced (LAD), and 7 resectable (RD) cases. Among the resectable cases, 2 patients had very high Ca19-9 levels, 4 had poor performance status precluding immediate surgery, and 1 had a suspected—but unconfirmed—distant metastasis. Clinical data including age, ECOG performance status, tumor location, resectability status, Ca19-9 levels, and surgical outcomes were collected. Survival was estimated with the Kaplan-Meier method and compared using the log-rank test. Results: All patients were treated with FOLFIRINOX. The median number of chemotherapy cycles before surgery decision was 7. A total of 24 patients (28.6%) underwent tumor resection: 6 RD, 9 BR, and 9 LAD cases. Resectability rates were similar between initially borderline and locally advanced cases. Patients whose Ca19-9 levels decreased by more than 55% were significantly more likely to undergo resection compared to those with lesser reductions (44% vs. 19%, respectively; p = 0.03). The overall survival (OS) for the entire cohort was 16.2 months. OS was 42.9 months for resected patients and 15.0 months for the 60 non-resected patients. Among non-resected patients, Ca19-9 reduction (greater or less than 55%) did not significantly affect survival (19 vs. 14 months, respectively). In contrast, survival benefit from surgery was only observed in patients whose Ca19-9 levels dropped by 55% or more (43 vs. 19 months). OS was similar (19 X 15 months) for resected (n=6) and non-resected (n=25) patients who did not achieve a ≥55% reduction in Ca19-9. Conclusions: These findings suggest that surgery following neoadjuvant/conversion chemotherapy should be considered primarily in patients with a Ca19-9 reduction of more than 55%.