Lung cancer continues to present an enormous global burden of morbidity and mortality, despite an increasing therapeutic armamentarium of chemotherapy and targeted agents. Recent research efforts have been directed towards identifying predictors of response to treatment, in order to facilitate the selection of patients likely to obtain the greatest benefit from specific therapeutic interventions, with the ultimate goal of providing customized therapy. A strong scientific basis exists for the use of markers to identify patients who are most likely to respond to biological and targeted therapies, based on characteristics such as tumour genotype and histology. Biomarkers have the potential to aid in patient stratification (risk assessment), treatment-response identification (surrogate markers), or differential diagnosis (identifying individuals who are likely to respond well to specific therapies). Numerous trials have demonstrated correlations between molecular biomarkers and the outcome of treatment with targeted therapies such as epidermal growth factor inhibitor tyrosine-kinase inhibitors in patients with non-small-cell lung cancer (NSCLC). The recently completed MarkER Identification Trial (MERIT) found some evidence of a link between the molecular profile of a tumour and the clinical response to erlotinib in patients with relapsed NSCLC. However, MERIT also highlighted the difficulties in obtaining adequate samples for the various procedures involved in genetic analyses in clinical trials. Routine clinical practice brings its own challenges relating to biopsy techniques and tissue availability and this has implications for the application of molecular analyses in treatment decision-making. Applying the lessons learned from tissue sampling and molecular testing in MERIT and other major NSCLC trials will be essential in paving the way for the routine use of biomarker analyses in clinical practice.
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