Circulating tumor cells (CTC) and KRAS mutant circulating free DNA (cfDNA) detection in peripheral blood as biomarkers in patients diagnosed with exocrine pancreatic cancer

Abstract

BackgroundPancreatic cancer remains one of the most difficult cancers to treat with the poorest prognosis. The key to improving survival rates in this disease is early detection and monitoring of disseminated and residual disease. However, this is hindered due to lack reliable diagnostic and predictive markers which mean that the majority of patients succumb to their condition within a few months.MethodsWe present a pilot study of the detection circulating free DNA (cfDNA) combined with tumor specific mutation detection by digital PCR as a novel minimally invasive biomarker in pancreatic ductal adenocarcinoma (PDAC). This was compared to the detection of CTC by the CellSearch® system and a novel CTC enrichment strategy based on CD45 positive cell depletion. The aim of the study was to assess tumor specific DNA detection in plasma and CTC detection as prognostic markers in PDAC.ResultsWe detected KRAS mutant cfDNA in 26 % of patients of all stages and this correlated strongly with Overall Survival (OS), 60 days (95 % CI: 19–317) for KRAS mutation positive vs 772 days for KRAS mutation negative (95 % CI: 416–1127). Although, the presence of CTC detected by the CellSearch® system did correlate significantly with OS, 88 days (95 % CI: 27–206) CTC positive vs 393 days CTC negative (95 % CI: 284–501), CTC were detected in only 20 % of patients, the majority of which had metastatic disease, whereas KRAS mutant cfDNA was detected in patients with both resectable and advanced disease.ConclusionsTumor specific cfDNA detection and CTC detection are promising markers for the management of patients with PDAC, although there is a need to validate these results in a larger patient cohort and optimize the detection of CTC in PDAC by applying the appropriate markers for their detection.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1779-7) contains supplementary material, which is available to authorized users.

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“…The system is quite sensitive for the detection of mutant DNA as about 0.5 ng corresponding to 37 copies can be detected by this technique. Pancreatic cancer patients that tested positive for any of the KRAS mutation in plasma cfDNA, using the Biorad system, had a significantly shorter overall survival than patients who tested negative for a mutation (60 days vs 772 days respectively) [4].…”

“…For detection of EGFR mutations, maximum authors use commercially available primer and probes and amplification by real time PCR. However, there have been instances of misdiagnosis of mutations in EGFR by routine EGFR mutation tests [4,48].…”

“…2). Similarly, primary tissue from pancreatic ductal adenocarcinoma patients is usually available only by fine-needle aspiration biopsies and there is a high chance of missing aggressive clones [4]. Besides, a standard protocol in cancer management involves periodic monitoring for progression and/or recurrence of the cancer.…”

Assessing the merits of existing pancreatic cancer biomarkers

“…Kulemann et al found CTCs in 73% of PDAC patients (n = 11); with CTCs being found in patients at every stage of the disease [34]. Earl et al measured CTCs in 20% of such cases (n = 35) [31] with six out of all seven patients with CTCs having metastases; one patient had a resectable tumour. These outcomes lead us to conclude that CTC may be a sensitive PDAC biomarker.…”

“…These outcomes lead us to conclude that CTC may be a sensitive PDAC biomarker. In addition, PDAC is poorly vascularised and its invasion is often limited to the liver, and only involves other organs at very advanced stages [31,35,36].…”