We took a longitudinal approach to molecularly assess treatment response via liquid biopsy, collecting multiple plasma samples throughout the course of treatment of 6 patients (2–8 samples from each): 4 patients with MNA neuroblastoma, and 3 patients with ALK variants in their tumor sample (2 with p.F1245I, and 1 with p.F1174L). The gene discussed is ALK; the disease is neoplasm.