title: Revisiting the technical validation of tumour biomarker assays: how to open a Pandora's box.
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.
authors.affiliation: Department of Biomedical Sciences and Human Oncology, University of Turin, Via Santena 7, 10126 Turin, Italy. caterina.marchio@unito.it
authors.forename: Caterina
authors.initials: C
authors.lastname: Marchiò
authors.forename: Mitch
authors.initials: M
authors.lastname: Dowsett
authors.forename: Jorge S
authors.initials: JS
authors.lastname: Reis-Filho
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis*; D019411:Clinical Laboratory Techniques / Q000379:methods* / Q000592:standards*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods / Q000592:standards; D009369:Neoplasms / Q000175:diagnosis*; D021141:Nucleic Acid Amplification Techniques / Q000379:methods / Q000592:standards; D054928:Validation Studies as Topic
chemical_list: D014408:Biomarkers, Tumor