TPMT and acute lymphoblastic leukemia: For instance, Van den Akker-van Marle et al. (2006) integrated thiopurine S-methyltransferase (TPMT) genotyping prior to scheduling 6-mercaptopurine in pediatric Acute Lymphoblastic Leukemia (ALL); the mean calculated cost has been estimated to average around €150,00 (Van den Akker-van Marle et al., 2006).