[Discrepancies between primary tumor and metastasis: impact on personalized medicine]

Molecular characterization of tumors is critical for the development and appropriate use of many anti-cancer agents. Potential discrepancies between primary tumor and secondary lesions lead to question on the optimal modalities for evaluation of biomarkers. In light of recent data, the need of iterative biopsies in metastatic setting has been suggested but technical and methodological limits in such analyses should not be ignored and this strategy can not be definitively validated. The evaluation of spatial and temporal variability of biomarkers in solid tumors should take into account tumoral context and therapeutic history of each patient for the development of personalized medicine in oncology.