Association of ALDH-expressing cancer stem cells with survival in patients with resected pancreatic adenocarcinoma treated with adjuvant chemoradiation.

Abstract

262 Background: We and others have identified aldehyde dehydrogenase (ALDH) activity as a marker of pancreatic cancer stem cells (or tumor-initiating cells). The presence of cancer stem cells (CSCs) has been associated with decreased survival and treatment resistance in pancreatic adenocarcinoma. We investigate the role of ALDH expression in predicting survival and patterns of disease recurrence in patients treated with chemoradiation (CRT) following pancreatectomy. Methods: Tissue microarrays using surgical specimens from 1998 to 2002 were stained for ALDH1 and scored as ALDH-positive or ALDH-negative by two expert pancreatic pathologists blinded to patient outcomes. Physician documentation and radiology reports were used to determine follow-up information. Time to local failure (TLF), time to distant metastases (TDM), progression-free survival (PFS), and overall survival (OS) were analyzed using SPSS software. Results: Previously we found that ALDH expression was associated with worse OS in a cohort of 269 patients with resected pancreatic adenocarcinoma (Rasheed, JNCI 2009). From this cohort, adjuvant treatment information was available for 87 patients with ALDH-negative tumors (48.6%) and 41 patients with ALDH-positive tumors (45.6%). In patients treated with adjuvant CRT, median overall survival was superior in the ALDH-negative cohort vs. the ALDH-positive cohort, 26.3 months vs. 18.2 months (p=0.011). Further, in patients treated with adjuvant CRT, ALDH-negative patients had statistically greater TLF, TDM, and PFS than their ALDH-positive counterparts (see table). On multivariate analysis, ALDH positive tumor staining (HR 1.94, p=0.004) and tumor grade (HR 1.54, p=0.041) predicted lower OS, and ALDH positive tumor staining (HR 1.83, p=0.008), tumor grade (HR 1.52, p=0.038), and tumor size >3 cm (HR 1.65, p=0.023) predicted decreased PFS. Conclusions: This study suggests that adjuvant CRT improves TLF, TDM, PFS, and OS in patients with localized pancreatic adenocarcinoma not enriched with ALDH-expressing CSCs. Laboratory studies will help elucidate the mechanisms of treatment resistance in ALDH expressing CSCs.