Why the Treatment Sequence Matters: Interplay Between Chemotherapy Cycles Received, Cumulative Dose Intensity, and Survival in Resected Early-stage Pancreas Cancer.

OBJECTIVE: To define the optimal threshold of perioperative chemotherapy completion and relative dose intensity (RDI) for patients with resected pancreatic ductal adenocarcinoma (PDAC). BACKGROUND: Many patients who undergo pancreatectomy for PDAC fail to initiate or complete recommended perioperative chemotherapy. The association between the amount of perioperative chemotherapy received and overall survival (OS) is not well-defined. METHODS: Single-institution analysis of 225 patients who underwent pancreatectomy for stage I/II PDAC (2010-2021). Associations between OS, chemotherapy cycles completed, and RDI were analyzed. RESULTS: Regardless of treatment sequence, completion of ≥67% of recommended cycles was associated with improved OS compared with no chemotherapy [median OS: 34.5 vs 18.1 months; hazard ratio (HR): 0.43; 95% CI: 0.25-0.74] and <67% of cycles (median OS: 17.9 months; HR: 0.39; 95% CI: 0.24-0.64). A near-linear relationship existed between cycles completed and the RDI received (ß = 0.82). A median RDI of 56% corresponded to the completion of 67% of cycles. Receipt of ≥56% RDI was associated with improved OS compared with no chemotherapy (median OS: 35.5 vs 18.1 months; HR: 0.44; 95% CI: 0.23-0.84) and <56% RDI (median OS: 27.2 months; HR: 0.44; 95% CI: 0.20-0.96). Neoadjuvant chemotherapy is associated with increased odds of receiving ≥67% of recommended cycles (odds ratio: 2.94; 95% CI: 1.45-6.26) and ≥56% RDI (odds ratio: 4.47; 95% CI: 1.72-12.50). CONCLUSIONS: Patients with PDAC who received ≥67% of recommended chemotherapy cycles or ≥56% cumulative RDI had improved OS. Neoadjuvant therapy was associated with increased odds of receiving ≥67% of cycles and ≥56% cumulative RDI and should be considered in all patients with resectable PDAC.