High-Dose Methotrexate Usage Without Drug-Level Monitoring in Advanced Pediatric Mature B-Cell Non-Hodgkin Lymphoma in a Resource-Limited Setting in Malawi.

Objective: Excellent survival for advanced (stages II with high lactate dehydrogenase, III, and IV) pediatric mature B-cell non-Hodgkin lymphoma (MB-NHL) has been achieved with intensive regimens, but adoption in sub-Saharan Africa is limited by inadequate supportive care. We provide real-world data on treating advanced MB-NHL with high-dose methotrexate (HD-MTX; ≥1,000 mg/m2/cycle) where real-time serum MTX monitoring is unavailable.

Methods: We identified two cohorts-a retrospective (January 2017-December 2020) cohort treated with 1,000 or 3,000 mg/m2/cycle of HD-MTX and a prospective (July 2022-July 2023) cohort-with a modified LMB96 protocol containing 3,000 mg/m2/cycle of HD-MTX. All doses of HD-MTX were given over 3 hours. Estimates of 12-month event-free survival (EFS) and overall survival (OS) were calculated with abandonment as an event. Clinical toxicity data were available for the prospective cohort.

Results: The retrospective cohort had 108 patients who received HD-MTX 1,000 mg/m2 (n = 98, 91%) or 3,000 mg/m2 per cycle. The 12-month EFS and OS were 39% (95% CI, 30 to 50) and 54% (95% CI, 44 to 64), respectively. HD-MTX at 3,000 mg/m2 had superior EFS: 69% (95% CI, 49 to 96) versus 33% (95% CI, 24 to 46), P = .004. The prospective cohort had 38 patients. Two ≥grade 3 mucositis, one acute kidney injury, and three treatment-related deaths (8%) occurred. Seven (18%) abandoned treatment. With a median follow-up of 14.5 months, 12-month EFS and OS were 45% (95% CI, 32 to 65) and 59% (95% CI, 45 to 79), respectively. Most relapses were stage IV: EFS 20% versus 51% (non-stage IV; P = .057). Severe malnutrition was associated with OS of 33% versus 58% (normal) or 76% (moderate; P = .055).

Conclusions: HD-MTX dosed at 3,000 mg/m2/cycle is feasible in low-resource settings where routine MTX monitoring is unavailable. Stage IV disease and severe malnutrition may contribute to poorer outcomes.