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Revisiting the technical validation of tumour biomarker assays: how to open a Pandora's box

Caterina Marchiò1*, Mitch Dowsett23 and Jorge S Reis-Filho3

Author Affiliations

1 Department of Biomedical Sciences and Human Oncology, University of Turin, Via Santena 7, 10126 Turin, Italy

2 Academic Department of Biochemistry, The Royal Marsden Hospital, Fulham Road, London, SW3 6JJ, UK

3 Molecular Pathology Laboratory, The Breakthrough Breast Cancer Research Centre, Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK

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BMC Medicine 2011, 9:41  doi:10.1186/1741-7015-9-41

Published: 19 April 2011

Abstract

A tumour biomarker is a characteristic that is objectively measured and evaluated in tumour samples as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. The development of a biomarker contemplates distinct phases, including discovery by hypothesis-generating preclinical or exploratory studies, development and qualification of the assay for the identification of the biomarker in clinical samples, and validation of its clinical significance. Although guidelines for the development and validation of biomarkers are available, their implementation is challenging, owing to the diversity of biomarkers being developed. The term 'validation' undoubtedly has several meanings; however, in the context of biomarker research, a test may be considered valid if it is 'fit for purpose'. In the process of validation of a biomarker assay, a key point is the validation of the methodology. Here we discuss the challenges for the technical validation of immunohistochemical and gene expression assays to detect tumour biomarkers and provide suggestions of pragmatic solutions to address these challenges.