Clinical significance and predictors of complete or near-complete histological response to preoperative chemoradiotherapy in patients with localized pancreatic ductal adenocarcinoma.

ABSTRACT

BACKGROUND: The clinical value and predictors of a favorable histological response to preoperative chemoradiotherapy (CRT) in pancreatic ductal adenocarcinoma (PDAC) remains undefined. OBJECTIVE: To assess the significance and predictors of a favorable histological response to preoperative CRT in patients with localized PDAC. METHODS: The study included 203 patients with localized PDAC undergoing curative-intent resection after CRT. The rate of R0 resection and overall survival (OS) and recurrence-free survival (RFS) were correlated with the grading of histological response to determine optimal stratification. Clinical factors associated with a significant histological response were evaluated using multivariate regression analysis. RESULTS: Among all patients, eight patients (3.9%) had a grade 4 (pCR); 40 (19.4%) had a grade 3 estimated rate of residual neoplastic cells <10% (near-pCR); and 155 (76.7%) had a grade 1/2 limited response. The 48 patients with pCR/near-pCR achieved significantly higher R0 resection rate (100%) than those with grade 1/2 (80.0%). The 5-year OS and RFS rates were significantly higher in the patients with pCR/near-pCR (45.3% and 36.5%) than in those with grade 1/2 (27.1% and 18.5%). Gemcitabine plus S-1 based CRT, serum CA19-9 level after CRT <83 U/mL, and interval from initial treatment to surgery ≥4.4 months were independent predictive factors for pCR/near-pCR. CONCLUSIONS: pCR or near-pCR to preoperative CRT contributed to achieving a high rate of R0 resection and improving survival for localized PDAC. The use of gemcitabine plus S-1 as a radiosensitizer, lower serum CA19-9 level after CRT, and longer preoperative treatment duration were significantly associated with pCR or near-pCR.