Histologic grading of the extent of residual carcinoma following neoadjuvant chemoradiation in pancreatic ductal adenocarcinoma: A predictor for patient outcome

BACKGROUND: Several grading schemes for the extent of residual tumor in posttreatment pancreaticoduodenectomy (PD) specimens have been proposed. However, the prognostic significance of these grading schemes is unknown. METHODS: Histopathologic slides of 223 cases who received neoadjuvant chemoradiation and PD were reviewed. The extent of residual tumor was graded using both the College of American Pathologists (CAP) and the Evans grading systems. The grading results were correlated with clinicopathological parameters and survival. RESULTS: Among the 223 patients, 6 patients (2.7%) showed pathologic complete response (pCR; CAP grade 0 or Evans grade IV), 36 cases (16.1%) had minimal residual tumor (CAP grade 1 or Evans grade III), 124 cases (55.6%) had moderate response (CAP grade 2 or Evans grade IIb), and 57 cases (25.6%) had poor response (CAP grade 3, where 18 had Evans grade I and 39 had Evans grade IIa response). Patients with pCR or minimal residual tumor (response group 1) had better survival rates than those with moderate and poor response (response group 2). Response group 1 patients had lower posttherapy tumor and American Joint Committee on Cancer stages and lower rates of lymph node metastasis, positive resection margin, and recurrence and/or metastasis. Grading the extent of residual tumor is an independent prognostic factor for overall survival in multivariate analysis. CONCLUSIONS: pCR or minimal residual tumor in posttreatment PD specimens correlate with better survival in patients with pancreatic ductal adenocarcinoma who received neoadjuvant therapy and PD. Histologic grading of the extent of residual tumor in PD specimen is an important prognostic factor in patients with pancreatic ductal adenocarcinoma who received neoadjuvant therapies.