Older age, CNS leukaemic involvement and induction tumour lysis increases the risk of methotrexate (MTX)-induced neurotoxicity in childhood acute lymphoblastic leukaemia/lymphoma: Experience from a tertiary care centre in South India.

Methotrexate (MTX), although an indispensable part of contemporary treatment protocols for childhood acute lymphoblastic leukaemia (ALL)/lymphomas (LBL) in improving outcomes, can lead to serious neurotoxicity with long-term consequences. The aetiopathogenesis, predisposing factors and treatment for MTX-induced neurotoxicity are not yet well defined. The aim of our study was to detect the incidence, risk factors and to assess the overall outcomes of MTX-induced neurotoxicity among large cohort of paediatric ALL/LBL patients treated on a uniform protocol. We conducted retrospective audit of medical records of 622 consecutive children (≤14 years) diagnosed with ALL and LBL between January 2018 and December 2022 and treated on modified BFM-95 protocol at the Department of Pediatric Oncology, Regional Cancer Centre, Thiruvananthapuram. Risk factors predisposing to MTX-induced neurotoxicity were identified using binary logistic regression analysis. Forty-three children were diagnosed with MTX-induced neurotoxicity with an incidence rate of 6.9%. More than two-thirds of them had high-grade MTX-induced neurotoxicity CTCAE v5.0 with a median age of 9 years (range: 9 months to 14 years). Almost half of them developed MTX neurotoxicity during Protocol M followed by Phase-Ib consolidation (15%). Majority of these patients (84%, 36/43) were challenged again with MTX, with 11% (4/36) developing recurrence. Fifteen per cent had persistent neurological deficits at last follow-up. Univariate analysis found older age (age > 5 years) (p < 0.001), T-cell phenotype (p = 0.040), tumour lysis syndrome during induction (p < 0.001), baseline renal problems prior to MTX exposure (p < 0.001) and CNS leukaemic involvement (p < 0.003) to be significantly associated with MTX neurotoxicity. On multivariate analysis, older age (>5 years), tumour lysis during induction and CNS leukaemia retained statistical significance (p < 0.05). Methotrexate-induced neurotoxicity during paediatric acute lymphoblastic leukaemia/lymphoma therapy is a transient phenomenon in majority and re-challenge with MTX is generally safe. Older age children who develop tumour lysis during induction and CNS leukaemic involvement are at increased risk for MTX-induced neurotoxicity during ALL/LBL treatment.