High-dose methotrexate (HDMTX) is used in the treatment of a range of adult and childhood cancers. Although HDMTX can provide effective anti-tumor activity with an acceptable safety profile for most patients, delayed methotrexate elimination (DME) develops in a minority of patients receiving HDMTX and may be accompanied by renal dysfunction and potentially life-threatening toxicity. A panel of European physicians with experience in the use of HDMTX as well as of glucarpidase convened to develop a series of consensus statements to provide practical guidance on the prevention and treatment of DME, including the use of glucarpidase. Robust implementation of supportive measures including hyperhydration and urine alkalinization emerged as critical in order to reduce the risk of DME with HDMTX treatment, with leucovorin rescue critical in reducing the risk of DME complications. Early recognition of DME is important to promptly implement appropriate treatment including, intensified hydration, high-dose leucovorin and, when appropriate, glucarpidase.

It has been suggested that 1–2% of acute promyelocytic leukemia (APL) patients present variant rearrangements of retinoic acid receptor alpha (RARα) fusion gene, with the promyelocytic leukaemia zinc finger (PLZF)/RAR_α being the most frequent. Resistance to all-trans-retinoic acid (ATRA) and arsenic trioxide (ATO) has been suggested in PLZF/RAR_α and other variant APLs. Herein, we analyze the incidence, characteristics, and outcomes of variant APLs reported to the multinational PETHEMA (Programa para el Tratamiento de Hemopatias Malignas) registry, and we perform a systematic review in order to shed light on strategies to improve management of these extremely rare diseases. Of 2895 patients with genetically confirmed APL in the PETHEMA registry, 11 had variant APL (0.4%) (9 PLZF-RAR_α and 2 NPM1-RAR_α), 9 were men, with median age of 44.6 years (3 months to 76 years), median leucocytes (WBC) 16.8 × 10⁹/L, and frequent coagulopathy. Eight patients were treated with ATRA plus chemotherapy-based regimens, and 3 with chemotherapy-based. As compared to previous reports, complete remission and survival was slightly better in our cohort, with 73% complete remission (CR) and 73% survival despite a high relapse rate (43%). After analyzing our series and performing a comprehensive and critical review of the literature, strong recommendations on appropriate management of variant APL are not possible due to the low number and heterogeneity of patients reported so far.

Introduction: High‐dose methotrexate (HDMTX) use can be limited by the development of acute kidney injury (AKI). Early AKI detection is paramount to prevent further renal injury and irreversible toxicities. This study sought to determine whether early elimination patterns of MTX would be useful as a biomarker of AKI in HDMTX treatment.Methods: This retrospective cohort study included two sites that collected ≥2 MTX levels within 16 h from completion of MTX infusion. Early levels were tagged and MTX elimination half‐life (t_½) were calculated from combinations of two of three different early time periods. Receiver operating characteristic (ROC) curves were synthesized for each elimination t_½ (biomarker) with respect to AKI and delayed methotrexate elimination (DME); the biomarker with the highest area under the ROC curve (AUC) was tested in a multiple variable logistic regression model.Results: Data from 169 patients who received a total of 556 courses of HDMTX were analyzed. ROC analysis revealed MTX elimination t_½ calculated from the second and third time periods had the highest AUC for AKI at 0.62 (interquartile range [IQR] 0.56–0.69) and DME at 0.86 (IQR 0.73–1.00). After adjusting for age, sex, dose (mg/m²), infusion duration, HDMTX course, and baseline estimated glomerular filtration rate, it remained significant for AKI with an OR of 1.29 and 95% confidence interval of 1.03–1.65.Conclusion: Early MTX elimination t_½ measured within 16 h of infusion completion was significantly associated with the development of AKI and serves as an early clearance biomarker that may identify patients who benefit from increased hydration, augmented leucovorin rescue, and glucarpidase administration.

Objectives: To determine the incidence of delayed methotrexate elimination (DME) and acute kidney injury (AKI) and their associations with clinical outcomes in patients receiving high-dose methotrexate (HDMTX) for cancer treatment. Methods: The HDMTX European Registry collected medical records data from 12 institutions in 5 European countries to investigate the clinical practice patterns of healthcare providers utilizing HDMTX for cancer treatment. Cancer types included were acute lymphoblastic leukemia (ALL), primary central nervous system lymphoma (PCNSL), non-Hodgkin lymphoma (NHL), osteosarcoma, and other CNS cancers. Primary endpoints were the incidence of DME and AKI; secondary endpoints were clinical outcomes, including hospital length of stay (LOS), delay in the subsequent course of treatment, methotrexate dose reduction, and omission of next course of treatment. Associations between the primary and secondary endpoints were analyzed with Chi-square and Wilcoxon rank-sum tests. Results: Among the 2501 total HDMTX courses analyzed, DME occurred in 302 courses (12.1%), and AKI in 384 courses (15.4%). DME incidence was highest in courses for PCNSL (18.2%) and NHL (17.2%); AKI incidence was highest in ALL courses (21.0%). Incidence of DME and AKI varied by age and methotrexate infusion duration among the different cancer types. Occurrence of DME was associated with longer delays prior to the next course of treatment, longer hospital LOS, and more frequent methotrexate dose reductions and dose omissions. Conclusions: While HDMTX is a very effective and safe treatment, administration of efficacious doses of methotrexate can lead to AKI and DME, and no single or combination of patient or treatment factors was found to reliably predict their occurrence. Thus, diligent monitoring of methotrexate levels is imperative for early detection and prompt management of nephrotoxicity in all settings where HDMTX treatment is administered.