The clinical utility of integrative genomics in childhood cancer extends beyond targetable mutations

We conducted integrative somatic-germline analyses by deeply sequencing 864 cancer-associated genes, complete genomes and transcriptomes for 300 mostly previously treated children and adolescents/young adults with cancer of poor prognosis or with rare tumors enrolled in the SickKids Cancer Sequencing (KiCS) program. Clinically actionable variants were identified in 56% of patients. Improved diagnostic accuracy led to modified management in a subset. Therapeutically targetable variants (54% of patients) were of unanticipated timing and type, with over 20% derived from the germline. Corroborating mutational signatures (SBS3/BRCAness) in patients with germline homologous recombination defects demonstrates the potential utility of PARP inhibitors. Mutational burden was significantly elevated in 9% of patients. Sequential sampling identified changes in therapeutically targetable drivers in over one-third of patients, suggesting benefit from rebiopsy for genomic analysis at the time of relapse. Comprehensive cancer genomic profiling is useful at multiple points in the care trajectory for children and adolescents/young adults with cancer, supporting its integration into early clinical management.

Di-genic inheritance of germline POLE and PMS2 pathogenic variants causes a unique condition associated with pediatric cancer predisposition

Polymerase proofreading-associated polyposis (PPAP) and Lynch syndrome, caused by mutated POLE and mismatch repair (MMR) genes, respectively, are associated with adult-onset cancer. PPAP and MMR-deficient tumors are both hypermutated, and each has a unique mutational signature. We describe a 4.5-year-old boy with multiple café au lait spots who presented with metastatic Sonic Hedgehog-activated medulloblastoma, with partial response to intensive chemotherapy and immunotherapy. Tumor showed microsatellite stability, loss of PMS2 nuclear expression, and an exceptionally high tumor mutational burden of 276 Mut/Mb. Germline molecular analysis revealed an inherited heterozygous pathogenic POLE variant and a de novo heterozygous PMS2 pathogenic variant. The tumor featured the MMR, POLE, and POLE+MMR mutational signatures. This is the first description of a di-genic condition, which we named "POL-LYNCH syndrome", manifested by an aggressive ultra-mutant pediatric medulloblastoma with a unique genomic signature. This article is protected by copyright. All rights reserved.

Trends in clinical development of pediatric cancer for PD-1 and PD-L1 inhibitors: an analysis of ClinicalTrials.gov

Compared with cytotoxic chemotherapy, radiotherapy, and surgery, positive findings have been acquired through the approach of blocking the programmed cell death protein 1 (PD-1) pathway with antibodies that exert inhibitory effects on PD-1 or cell death protein ligand 1 (PD-L1). Results from clinical trials showed great potential in adult patients with cancers, such as melanoma, non-small cell carcinoma, and nasopharyngeal carcinoma. However, studies of checkpoint inhibitors specifically targeting PD-1/PD-L1 in pediatric patients are limited. We evaluated ongoing clinical trials using PD-1 or PD-L1 inhibitors alone or in combination with other therapies to treat pediatric cancer. The proportion of PD-1/PD-L1 combination clinical trials has increased since 2018; the three most common trials over the past 2 years used CTLA-4 monoclonal antibodies, chemotherapy, and therapies that target the vascular endothelial growth factor axis. This commentary aimed to provide trends and specific insights into methods for conducting clinical trials of immunotherapy in the pediatric population.