Genotyping circulating tumor DNA of pediatric Hodgkin lymphoma.

We used hybrid capture-targeted next-generation sequencing of circulating cell-free DNA (ccfDNA) of pediatric Hodgkin lymphoma (PHL) patients to determine pathogenic mechanisms and assess the clinical utility of this method. Hodgkin-Reed/Sternberg (HRS) cell-derived single nucleotide variants, insertions/deletions, translocations and VH-DH-JH rearrangements were detected in pretherapy ccfDNA of 72 of 96 patients. Number of variants per patient ranged from 1 to 21 with allele frequencies from 0.6 to 42%. Nine translocation breakpoints were detected. Genes involved in JAK/STAT, NFkB and PI3K signaling and antigen presentation were most frequently affected. SOCS1 variants, mainly deletions, were found in most circulating tumor (ct) DNAs, and seven of the nine translocation breakpoints involved SOCS1. Analysis of VH-DH-JH rearrangements revealed an origin of PHL HRS cells from partially selected germinal center B cells. Amounts of pretherapy ctDNA were correlated with metabolic tumor volumes. Furthermore, in all ccfDNA samples of 43 patients with early response assessment quantitative qPET < 3, indicative of a favorable clinical course, ctDNA was not detectable. In contrast, in five of six patients with qPET > 3, indicative of an unfavorable clinical course, ctDNA remained detectable. ccfDNA analysis of PHL is thus a suitable approach to determine pathogenic mechanisms and monitor therapy response.

Targeted Next-Generation Sequencing Is a Sensitive Tool for Differential Diagnosis of Myelodysplastic Syndromes in Bone Marrow Trephines.

Myelodysplastic syndromes are hematological neoplasias in which immunohistologic examination of bone marrow trephines is important for a definite diagnosis. Unequivocal distinction from reactive bone marrow changes is, however, sometimes difficult. Because neoplastic clones in myelodysplastic syndrome carry mutations in recurrent genes, mutation detection by targeted next-generation sequencing may be a useful support for differential diagnosis. To elucidate the accuracy of this approach in the clinical diagnostic setting, we analyzed single and consecutive bone marrow trephines processed for immunohistologic examination from 145 patients by targeted next-generation sequencing of 12 genes recurrently mutated in myelodysplastic syndromes. Of 110 patients with immunohistologic unequivocal diagnosis, 41 of 47 with myelodysplastic syndrome carried mutations. In 14 consecutive samples available from these patients, remissions were accompanied by loss of mutations and ongoing disease with persisting mutations. Of 35 samples with indefinite immunohistologic appearance, 22 developed clinical unequivocal myelodysplastic syndrome in the further course, and 19 carried mutations already in the initial biopsy, which persisted in consecutive samples available from 13 patients. No mutation was detected in any initial and consecutive sample of 13 patients with indefinite immunohistologic appearance without clinical unequivocal myelodysplastic syndrome in the further course. We conclude that targeted next-generation sequencing is an accurate tool for differential diagnosis of myelodysplastic syndrome in the clinical diagnostic setting.