Cumulative incidence and comparison of 6-MP dose in patients with SMNs after ALL. (A) Cumulative incidence of SMNs in 438 children in TCCSG L04-16 who received ALL therapy was significantly higher in patients with NUDT15 variants (3.0% at 7 years) than in those with wild-type alleles (0.3%; P = .045). P value was calculated using the Gray test. (B) Average daily dose of 6-MP in maintenance therapy for patients with SMNs with a NUDT15 heterozygous variant was significantly higher than the dose administered to control (CNTL) patients with the same NUDT15 genotype, but they did not develop SMNs after 6-MP–containing therapy in a previous study (P = .045). P value was calculated using the Mann-Whitney U test.