Germline Variant Burden Warrants Universal Genetic Testing in Pediatric Myeloid Leukemia

Causal germline genetic variants are frequently detected in young (under age 40) patients presenting with myelodysplastic syndromes (MDS) or bone marrow failure (BMF), where progression to acute myeloid leukemia (AML) contributes substantially to mortality in these patients. We reasoned that de novo pediatric AML, which shares clinical and biological characteristics, might also share germline genetic risk variants. We investigated germline variants in a large cohort (n=365) of pediatric AML patients with whole-genome sequencing (WGS), 29 with matched marrow-derived stromal cells, and 336 with matched remission marrow samples. Variants were deemed "likely germline" based on variant allele frequency (VAF) across available samples. Following American College of Medical Genetics and Genomics (ACMG) and Association of Molecular Pathology (AMP) guidelines, we annotated pathogenic/likely pathogenic (P/LP) variants in 555 genes linked to leukemia risk. P/LP variants were identified in 5.5% (95% CI: (3.3%,7.9%)) of patients in genes linked to familial myeloid malignancy and an additional 3.3% (95% CI: (1.6%,5.2%)) of patients in genes conferring risk to lymphoid malignancy or solid tumors. The large cohort enabled burden testing, which we employed by comparing loss-of-function variants between patients and 2504 control subjects from the 1000 Genomes Project. There was a 6.9-fold (95% CI: (3.1,14.9)) increase in loss-of-function variants in genes implicated in myeloid malignancy risk, a 2.4-fold (95% CI: (1.7,3.2)) increase in candidate risk genes, and a 1.6-fold (95% CI: (1.1,2.3)) increase in randomly-selected genes. We then assembled cohorts totaling 4,622 pediatric and adult patients with acute leukemia or MDS from 10 published studies, and compared P/LP variant burdens across age and diagnosis. The prevalence of germline variants in myeloid malignancies across age groups exceeds 5% consistently and with high confidence. Because the National Comprehensive Cancer Network recommends that all patients receive screening if their pre-test germline variant probability exceeds 5%, our results support germline genetic variant testing as an integral component of diagnostic work-up for myeloid malignancies, including donor selection for stem cell transplantation.