Pathological staging in postneoadjuvant pancreatectomy for pancreatic cancer: implications for adjuvant therapy.

Background: It is unclear whether pathological staging is significant prognostically and can inform the delivery of adjuvant therapy after pancreatectomy preceded by neoadjuvant therapy. Methods: This multicentre retrospective study included patients who underwent pancreatectomy for pancreatic ductal adenocarcinoma after neoadjuvant treatment at two Italian centres between 2013 and 2017. T and N status were assigned in accordance with the seventh and eighth editions of the AJCC staging system, as well as according to a modified system with T status definition combining extrapancreatic invasion and tumour size. Patients were then stratified by receipt of adjuvant therapy. Survival analysis and multivariable interaction analysis of adjuvant therapy with pathological parameters were performed. The results were validated in an external cohort from the USA. Results: The developmental set consisted of 389 patients, with a median survival of 34.6 months. The modified staging system displayed the best prognostic stratification and the highest discrimination (C-index 0.763; 1-, 2- and 3-year time-dependent area under the curve (AUC) 0.746, 0.722, and 0.705; Uno's AUC 0.710). Overall, 67.0 per cent of patients received adjuvant therapy. There was no survival difference by receipt of adjuvant therapy (35.0 versus 36.0 months; P = 0.772). After multivariable adjustment, interaction analysis suggested a benefit of adjuvant therapy for patients with nodal metastases or with tumours larger than 2 cm with extrapancreatic extension, regardless of nodal status. These results were confirmed in the external cohort of 216 patients. Conclusion: Modified staging with a T status definition combining extrapancreatic invasion and tumour size is associated with better prognostic segregation after postneoadjuvant pancreatectomy. This system allows identification of patients who might benefit from adjuvant therapy. [ABSTRACT FROM AUTHOR]