C-Reactive Protein-to-Albumin Ratio as a Predictive Indicator for Evaluating Tolerability in S-1 Adjuvant Chemotherapy after Curative Surgery for Pancreatic Cancer: An External Validation Cohort Study

S-1 in adjuvant chemotherapy (AC) administration after pancreatic cancer (PC) surgery has been standardized in Japan. The Ehime study confirmed that a postoperative higher C-reactive protein-to-albumin ratio (CAR) value predicted the risk of adverse event (AE)-related S-1 non-completion as an AC in patients with PC after curative surgery. This study aimed to investigate the index to predict S-1 tolerance among patients who underwent curative surgery for PC (the Dokkyo study). This retrospective validation cohort study included 172 patients at the Department of Hepato-Biliary Pancreatic Surgery, Dokkyo Medical University, Japan, from January 2010 to December 2022. All patients underwent nutritional screening using the postoperative CAR. S-1 completion status and its effect on prognosis were systematically followed up and investigated. We conducted a statistical analysis of predictive markers to investigate their association with S-1 completion. Patients were categorized into the S-1 completion (N = 91) and non-completion (N = 81) groups. The S-1 completion group demonstrated a significantly lower CAR than the S1 non-completion group. Moreover, the current study revealed a significant difference in the S-1 completion rate, applying the CAR cutoff value of 0.05 established in the Ehime study. Additionally, univariate and multivariate analyses confirmed that a CAR of