Therapy-related mutational signatures in subsequent neoplasms among survivors of childhood cancer

Childhood cancer survivors have heightened risk of developing subsequent neoplasms (SNs) related to therapy. We analyzed whole-genome, exome and RNA sequencing of 200 breast, meningioma, and thyroid SNs, which developed a median of 26.4 years after childhood cancer, among 160 survivors. Meningioma and thyroid SNs were enriched for driver gene rearrangements compared to de novo tumors, including NF2-disrupting alterations and kinase fusions potentially induced by radiation. Radiation correlated with increased insertion-deletion signature ID5. Nitrogen mustard treatment correlated with elevated “flat” signature SBS5 in breast and meningioma SNs; in vitro, these agents caused an unresolved flat signature associated with multiple flat COSMIC signatures. In meningioma, platinum therapy correlated with NF2 splice-site variants. Analysis of 19 multi-sample survivors revealed intrapatient heterogeneity in meningioma, including clonally independent tumors. These results demonstrate the long-term impact of childhood cancer treatment on the genomes of SNs developing in adulthood, which may guide SN treatment and prevention.