Bayesian Approach to Understand the Association Between Treatment Down-staging and Survival for Patients With Pancreatic Adenocarcinoma.

OBJECTIVE: To evaluate the association between staging concordance, treatment sequencing, and response to neoadjuvant therapy (NAT) on the survival of patients with pancreatic ductal adenocarcinoma (PDAC). SUMMARY OF BACKGROUND DATA: NAT is increasingly utilized in the management of patients with PDAC, but it is unclear whether its benefit is contingent on tumor down-staging. METHODS: This was a cohort study of stage I-III PDAC patients in the National Cancer Database (2006-2015) treated with upfront resection or NAT followed by surgery. We determined staging concordance using patients' clinical and pathological staging data. For NAT patients, we used Bayesian analysis to ascertain staging concordance accounting for down-staging. RESULTS: Among 16,597 patients treated at 979 hospitals, 13,982 had an upfront resection and 2,615 NAT followed by surgery. Overall survival (OS) at 5-years ranged from 26.0% (95% CI 24.9%-27.1%) among cT1-2N0 patients to 18.6% (17.9%-19.2%) among cT1-3N+ ones. Patients with cT3-4 or cN+ tumors had improved OS after NAT compared to upfront surgery (all p< 0.001), while there was no difference among patients with cT1-2N0 (P = 0.16) disease. Relative to accurately staged cT1-2-3N+ or cT4 patients treated with upfront surgery, NAT was associated with a lower risk of death [HR 0.46 (0.37-0.57) for N+; HR 0.56 (0.40-0.77) for T4 disease], even among those without tumor down-staging [HR 0.81 (0.73-0.90) for N+; HR 0.48 (0.39-0.60) for T4]. CONCLUSIONS: NAT is associated with improved survival for PDAC, particularly for patients with more advanced disease and regardless of down-staging. Consideration should be given to recommending NAT for all PDAC patients.