[Liquid biopsy in oncology: A consensus statement of the Spanish Society of Pathology and the Spanish Society of Medical Oncology].

The proportion of cancer patients with tumours that harbour a potentially targetable genomic alteration is increasing considerably. The diagnosis of these genomic alterations can lead to tailoring of treatment, at the onset of disease or during progression, as well as providing additional, predictive information on the efficacy of immunotherapy. However, in up to 25% of cases, the initial tissue biopsy is inadequate for precision oncology and, in many cases, tumour genomic profiling at progression is not possible due to technical limitations of obtaining new tumour tissue specimens. Efficient diagnostic alternatives are therefore required for molecular stratification, such as liquid biopsy. This technique enables the evaluation of the tumour genomic profile dynamically and as well as capturing intra-patient genomic heterogeneity. To date, there are several diagnostic techniques available for use in liquid biopsy, each with different precision and performance levels. The objective of this consensus statement of the Spanish Society of Pathology (SEAP) and the Spanish Society of Medical Oncology (SEOM) is to evaluate the viability and effectiveness of the different methodological approaches of liquid biopsy in cancer patients, and the potential application of this method to current clinical practice. The experts contributing to this consensus statement agree that, according to current evidence, liquid biopsy is an acceptable alternative to tumour tissue biopsy for the study of biomarkers in various clinical settings. It is therefore important to standardise pre-analytical and analytical procedures to ensure reproducibility and to generate structured and accessible clinical reports. It is essential to appoint multidisciplinary tumour molecular committees to oversee these processes and to enable the most suitable therapeutic decisions for each patient according to the genomic profile.