Impact of Disseminated Neuroblastoma Cells on the Identification of the Relapse-Seeding Clone.

Purpose: Tumor relapse is the most frequent cause of death in stage 4 neuroblastomas. Since genomic information on the relapse precursor cells could guide targeted therapy, our aim was to find the most appropriate tissue for identifying relapse-seeding clones.Experimental design: We analyzed 10 geographically and temporally separated samples of a single patient by SNP array and validated the data in 154 stage 4 patients.Results: In the case study, aberrations unique to certain tissues and time points were evident besides concordant aberrations shared by all samples. Diagnostic bone marrow-derived disseminated tumor cells (DTCs) as well as the metastatic tumor and DTCs at relapse displayed a 1q deletion, not detected in any of the seven primary tumor samples. In the validation cohort, the frequency of 1q deletion was 17.8%, 10%, and 27.5% in the diagnostic DTCs, diagnostic tumors, and DTCs at relapse, respectively. This aberration was significantly associated with 19q and ATRX deletions. We observed a significant increased likelihood of an adverse event in the presence of 19q deletion in the diagnostic DTCs.Conclusions: Different frequencies of 1q and 19q deletions in the primary tumors as compared with DTCs, their relatively high frequency at relapse, and their effect on event-free survival (19q deletion) indicate the relevance of analyzing diagnostic DTCs. Our data support the hypothesis of a branched clonal evolution and a parallel progression of primary and metastatic tumor cells. Therefore, searching for biomarkers to identify the relapse-seeding clone should involve diagnostic DTCs alongside the tumor tissue. Clin Cancer Res; 23(15); 4224-32. ©2017 AACR.