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2007 Program and Abstracts | 2007 Posters
Prediction of Lymph Node Status After Neoadjuvant Radiochemotherapy (RCT) in Rectal Cancer By Genome Microarray Analysis
Dermot T. Mcdowell*1, Fraser M. Smith1, Cian Muldoon2, Charles Gillham3, Eoin Gaffney2, Donal Hollywood3, Brian Mehigan1, Richard Stephens1, M John Kennedy3, John V. Reynolds1
1Department of Academic Surgery, St James's Hospital, Dublin 8, Ireland; 2Department of Pathology, St James's Hospital, Dublin 8, Ireland; 3Academic Unit of Clinical and Molecular Oncology, St James's Hospital, Dublin 8, Ireland

Aims:The identification of biomarkers that can accurately predict the nodal status of rectal cancer after RCT may allow for a select group of patients to avoid laparotomy, by either undergoing local excision of their cancer or by observation management alone. This study aims to identify potential biomarkers in fresh, pre-treatment biopsies using gene expression profiling.
Methods:Fresh pre-RCT rectal cancer biopsies were obtained and placed in RNAlaterÒ. Total RNA was prepared, reverse transcribed and used to generate digoxigenin-labelled cRNA fragments. Samples were hybridised to whole genome expression microarrays (Applied Biosystems). Following data normalisation, with bioinformatic software, the patients were sub-divided according to whether they had positive or negative lymphatic spread. Resultant gene expression profiles were validated by real time quantitative PCR and checked for statistical correlation between methods.
Results:High quality RNA, suitable for gene microarray analysis was obtained in 15 patients. Lymph node positive and negative tumours were seen in 7 and 8 patients respectively. Data analysis using Bioconductor-R bioinformatics software package and SPSS (v12.0) was performed. Eighty-nine genes differentiated LNN from LNP patients (p<0.01). These include genes involved in apoptosis, cell adhesion, cell cycle control and proliferation. We are performing gene networking analysis.
Conclusions:This preliminary study has identified a panel of biomarkers that seem to be associated with the nodal status of rectal cancer patients after RCT. These genes require further validation but may lead to improved treatment strategies. These markers are currently being assessed prospectively in a further cohort of patients. Patients who have a complete clinical response and are predicted LNN might be safely managed by observation alone post RCT.

2007 Program and Abstracts | 2007 Posters
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