Evaluation of the significance of adjuvant chemotherapy in patients with stage ⅠA pancreatic ductal adenocarcinoma

Background: Although adjuvant chemotherapy is considered a standard treatment for resected pancreatic ductal adenocarcinoma (PDAC), its utility in stage ⅠA patients is unclear. We aimed to investigate the recurrence rate, surgical outcome, prognostic factors, effectiveness of adjuvant chemotherapy, and determination of groups in whom adjuvant chemotherapy is effective in patients with stage ⅠA PDAC. Methods: We retrospectively analyzed 73 patients who underwent pancreatectomy and were pathologically diagnosed with stage ⅠA PDAC between 2000 and 2018. We evaluated the relation between clinicopathological factors, recurrence rates, and outcomes such as the recurrence-free and disease-specific survival rates (RFS and DSS, respectively). Results: The 5-year RFS and DSS rates were 52% and 58%, respectively. In multivariate analysis, a platelet-to-lymphocyte ratio (PLR) ≥ 170, prognostic nutrition index (PNI) < 47.5, and pathological grade 2 or 3 constituted risk factors for a shorter DSS (hazard ratios: 4.7, 4.6, and 4.1, respectively). Patients with 0–1 of these risk factors (low-risk group; n = 47) had significantly higher 5-year DSS rates than those with 2–3 risk factors (high-risk group; n = 26) (80% vs. 23%; P < 0.001). Patients in the low-risk group showed similar 5-year RFS rates regardless of whether they received or not adjuvant chemotherapy (75% vs 70%, respectively; P = 0.49). Contrarily, high-risk patients who underwent adjuvant chemotherapy had higher 5-year RFS rates than those who did not receive adjuvant chemotherapy (32% vs 0%; P = 0.045). Conclusions: In stage IA PDAC, adjuvant chemotherapy seems to be effective only in a subgroup of high-risk patients.