Despite this, the detection in blood of the ALK status and ALK mutations holds certain limits (Table 1). The detection of CTCs is not a standardized approach of daily practice and reproducibility requires good technical skills. Moreover, CTC detection techniques are not available in all institutions and thus not easily accessible to all patients. The detection of an ALK rearrangement in plasma or in platelets can only be performed if the pre-analytical phases are perfectly controlled (appropriate tubes to collect and package the blood, short delay for transfer to the laboratory, well established centrifugation protocols, storage of plasma or platelets at low temperature). Beyond mastering the techniques, it should be noted that the amount of CTCs or plasma RNA or RNA associated with platelets can be very variable depending on the patient and the tumor biology and the tumor mass. Thus, certain patients, even during the metastatic phase, can have a very low number of CTCs and/or a low amount of plasma RNA. In addition, it is possible that 10 mL of blood is not sufficient to isolate enough quantity of tumor RNA, particularly for NGS methods.