In two aspects, the deletions of radiation-associated cancers resembled those of BRCA1 or BRCA2 germline-deficient breast tumours (Supplementary Fig. 2): enrichment for deletions >2–3 bp in length and significantly higher rates of microhomology at the breakpoint junction (P=2 × 10−16, Kolmogorov–Smirnov test)27. This evidence concerns the gene BRCA1 and cancer.