Jacob Nersting1, Stine Nygaard Nielsen2, Kathrine Grell2,3, Maria Paerregaard2, Jonas Abrahamsson4, Bendik Lund5, Olafur Gisli Jonsson6, Kaie Pruunsild7, Goda Vaitkeviciene8, Jukka Kanerva9, Kjeld Schmiegelow2,10. 1. Department of Pediatrics and Adolescent Medicine, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark. jacob.nersting@regionh.dk. 2. Department of Pediatrics and Adolescent Medicine, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, 2100, Copenhagen, Denmark. 3. Section of Biostatistics, Department of Public Health, University of Copenhagen, Copenhagen, Denmark. 4. Department of Pediatrics, Institution for Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. 5. Department of Pediatrics, St. Olavs Hospital, Trondheim University Hospital, Trondheim, Norway. 6. Department of Pediatrics, Landspitali University Hospital, Reykjavík, Iceland. 7. Tallinn Children's Hospital, Tallinn, Estonia. 8. University Hospital Santariskiu Klinikos, Vilnius, Lithuania. 9. Children's Hospital, Helsinki University Central Hospital, University of Helsinki, Helsinki, Finland. 10. Institute of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
Abstract
PURPOSE: Methotrexate polyglutamates (MTXpg) facilitate incorporation of thioguanine nucleotides into DNA (DNA-TG, the primary cytotoxic thiopurine metabolite and outcome determinant in MTX/6-mercaptopurine treatment of childhood ALL). We hypothesized that mapping erythrocyte levels of MTXpg with 1-6 glutamates and their associations with DNA-TG formation would facilitate future guidelines for maintenance therapy dosing. METHODS AND RESULTS: Summed MTX with 1-6 glutamates resolved by LCMS [median (interquartile): 5.47 (3.58-7.69) nmol/mmol hemoglobin] was in agreement with total MTX by radio ligand assay. In 16,389 blood samples from 1426 ALL maintenance therapy patients, MTXpg3 21.0 (15.2-27.4)% was the predominant metabolite, and MTXpg1 (the maternal drug) constituted 38.6 (27.2-50.2)% of MTXpg1-6. All subsets correlated; the strongest associations were between metabolites with similar polyglutamate lengths. Correlations of MTXpg1 with MTXpg2 and MTXpg3,4,5,6 were rs = 0.68 and rs = 0.25-0.42, respectively. Intercorrelations of MTXpg3,4,5,6 were all rs ≥ 0.51. MTXpg4 accounted for 29.8 (24.7-33.3)% of MTXpg3-6, yet explained 96% of the summed MTXpg3-6 variation. MTXpg1-4, MTXpg1-6, MTXpg2-6 and MTXpg3 were all associated with DNA-TG levels (p < 0.00001), but collinearity precluded identification of the most informative subset. CONCLUSIONS: Measuring erythrocyte MTXpg4 simplifies and can replace longer chain MTXpg monitoring. Resolving individual MTXpg identifies samples that are unsuitable for dose guidance due to high levels of MTXpg1 remaining in the plasma fraction because of recent MTX intake. All tested MTXpg subsets correlated with DNA-TG and may be used for ALL maintenance therapy dose adjustments, but the most informative subset remains to be identified.
PURPOSE:Methotrexate polyglutamates (MTXpg) facilitate incorporation of thioguanine nucleotides into DNA (DNA-TG, the primary cytotoxic thiopurine metabolite and outcome determinant in MTX/6-mercaptopurine treatment of childhood ALL). We hypothesized that mapping erythrocyte levels of MTXpg with 1-6 glutamates and their associations with DNA-TG formation would facilitate future guidelines for maintenance therapy dosing. METHODS AND RESULTS: Summed MTX with 1-6 glutamates resolved by LCMS [median (interquartile): 5.47 (3.58-7.69) nmol/mmol hemoglobin] was in agreement with total MTX by radio ligand assay. In 16,389 blood samples from 1426 ALL maintenance therapy patients, MTXpg3 21.0 (15.2-27.4)% was the predominant metabolite, and MTXpg1 (the maternal drug) constituted 38.6 (27.2-50.2)% of MTXpg1-6. All subsets correlated; the strongest associations were between metabolites with similar polyglutamate lengths. Correlations of MTXpg1 with MTXpg2 and MTXpg3,4,5,6 were rs = 0.68 and rs = 0.25-0.42, respectively. Intercorrelations of MTXpg3,4,5,6 were all rs ≥ 0.51. MTXpg4 accounted for 29.8 (24.7-33.3)% of MTXpg3-6, yet explained 96% of the summed MTXpg3-6 variation. MTXpg1-4, MTXpg1-6, MTXpg2-6 and MTXpg3 were all associated with DNA-TG levels (p < 0.00001), but collinearity precluded identification of the most informative subset. CONCLUSIONS: Measuring erythrocyte MTXpg4 simplifies and can replace longer chain MTXpg monitoring. Resolving individual MTXpg identifies samples that are unsuitable for dose guidance due to high levels of MTXpg1 remaining in the plasma fraction because of recent MTX intake. All tested MTXpg subsets correlated with DNA-TG and may be used for ALL maintenance therapy dose adjustments, but the most informative subset remains to be identified.
Authors: Linea Natalie Toksvang; Bodil Als-Nielsen; Christopher Bacon; Ruta Bertasiute; Ximo Duarte; Gabriele Escherich; Elín Anna Helgadottir; Inga Rinvoll Johannsdottir; Ólafur G Jónsson; Piotr Kozlowski; Cecilia Langenskjöld; Kristi Lepik; Riitta Niinimäki; Ulrik Malthe Overgaard; Mari Punab; Riikka Räty; Heidi Segers; Inge van der Sluis; Owen Patrick Smith; Marion Strullu; Goda Vaitkevičienė; Hilde Skuterud Wik; Mats Heyman; Kjeld Schmiegelow Journal: BMC Cancer Date: 2022-05-02 Impact factor: 4.638