"As expected TPMT was the main cause of severe hematotoxicity in 31% of patients who were either TPMT deficient (10%) or heterozygous carriers of TPMT variants (21%). By comparison NUDT15 genetic polymorphism was identified in 14 (13%) patients including one novel variant (p.Met1Ile). Six percent of patients with severe toxicity carried variants in both TPMT and NUDT15."xsd:string