ALK rearrangements and ALK mutations can be detected with a LB. The specificity of detection is very good with CTCs, plasma and platelets. As described above, different approaches exist and the combination of these approaches might increase the chance to detect ALK rearrangements and ALK mutations. However, future efforts should be done to compare these methods in the same cohorts of patients to see the potentiality to use them simultaneously to increase the number of ALK positive blood samples. In the event of a positive result in blood samples, correlation with the results obtained with tissues is excellent. In contrast, the sensitivity is variable depending on the approach used, notably for techniques developed with plasma free RNA. The benefit of LB is the same as for the detection of EGFR mutations in blood: (i) for detection of an ALK rearrangement when it is impossible to perform a tissue biopsy or if the tissue sample is degraded or not exploitable; (ii) for early detection of ALK mutations associated with resistance to treatment leading to a rapid change in the therapeutic strategy; and (iii) for monitoring of the efficacy of treatments targeting an ALK rearrangement when this genomic alteration is lost or inversely reappears in blood.