Locally advanced pancreatic cancer: association between prolonged preoperative treatment and lymph-node negativity and overall survival.

Abstract

Treatment of patients with locally advanced/borderline resectable (LA/BR) pancreatic ductal adenocarcinoma (PDAC) is not standardized. To (1) perform a detailed survival analysis of our institution's experience with patients with LA/BR PDAC who were downstaged and underwent surgical resection and (2) identify prognostic biomarkers that may help to guide a decision for the use of adjuvant therapy in this patient subgroup. Retrospective observational study of 49 consecutive patients from a single institution during 1992-2011 with American Joint Committee on Cancer stage III LA/BR PDAC who were initially unresectable, as determined by staging computed tomography and/or surgical exploration, and who were treated and then surgically resected. Clinicopathologic variables and prognostic biomarkers SMAD4, S100A2, and microRNA-21 were correlated with survival by univariate and multivariate Cox proportional hazard modeling. All 49 patients were deemed initially unresectable owing to vascular involvement. After completing preoperative chemotherapy for a median of 7.1 months (range, 5.4-9.6 months), most (75.5%) underwent a pylorus-preserving Whipple operation; 3 patients (6.1%) had a vascular resection. Strikingly, 37 of 49 patients were lymph-node (LN) negative (75.5%) and 42 (85.7%) had negative margins; 45.8% of evaluable patients achieved a complete histopathologic (HP) response. The median overall survival (OS) was 40.1 months (range, 22.7-65.9 months). A univariate analysis of HP prognostic biomarkers revealed that perineural invasion (hazard ratio, 5.5; P=.007) and HP treatment response (hazard ratio, 9.0; P=.009) were most significant. Lymph-node involvement, as a marker of systemic disease, was also significant on univariate analysis (P=.05). Patients with no LN involvement had longer OS (44.4 vs 23.2 months, P=.04) than LN-positive patients. The candidate prognostic biomarkers, SMAD4 protein loss (P=.01) in tumor cells and microRNA-21 expression in the stroma (P=.05), also correlated with OS. On multivariate Cox proportional hazard modeling of HP and prognostic biomarkers, only SMAD4 protein loss was significant (hazard ratio, 9.3; P=.004). Our approach to patients with LA/BR PDAC, which includes prolonged preoperative chemotherapy, is associated with a high incidence of LN-negative disease and excellent OS. After surgical resection, HP treatment response, perineural invasion, and SMAD4 status should help determine who should receive adjuvant therapy in this select subset of patients.