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.

Pharmacotherapeutic Management of Pediatric Lymphoma.

Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) comprise approximately 15% of all childhood malignancies. Cure rates for both lymphoma entities have evolved tremendously during the last couple of decades, raising the 5-year survival rates to almost 100% for HL and to 85% for NHL. The mainstay therapy for both malignancies is still chemotherapy-with different regimens recommended for different types of disease. In HL, combined modality treatment, i.e., chemotherapy followed by radiotherapy, has long been the standard regimen. In order to reduce long-term side effects, such as second malignancies, most major pediatric HL consortia have studied response-based radiotherapy reduction strategies over the last 3 decades. For recurrent disease, high-dose chemotherapy followed by an autologous or an allogeneic hematopoietic stem-cell transplant is an option. No targeted agents have yet gained regulatory approval for use in pediatric patients with lymphoma. For adult lymphoma patients, the CD20 antibody rituximab and the CD30 antibody-drug conjugate brentuximab vedotin are targeted agents used regularly in first- and second-line treatment regimens. More recently, immune checkpoint inhibitors, phosphatidyl-inositol-3-kinase inhibitors, and Bruton's tyrosine kinase inhibitors appear to be very promising new treatment options in adult lymphoma. Here, we discuss the current experience with these types of agents in pediatric lymphoma patients.