Intensifying Methotrexate (MTX) Dosage Reduces Treatment Failure in Adults with Burkitt or Burkitt-Like Leukaemia/Lymphoma (BL) Treated with an Adapted BFM Protocol.

The use of short-duration intensive combination chemotherapy protocols has improved survival in adults with Burkitt/Burkitt-like leukaemia and lymphoma (BL). Systemic methotrexate (MTX) is an integral component of these regimens, but the dosage varies between treatment schedules, and the precise dose required to optimise tumour-kill without causing severe toxicity is not known. In this study of 66 adults with sporadic BL, we have investigated whether the dosing intensity of MTX can influence treatment failure (defined as disease relapse or resistance to treatment, or death due to therapy). There were 49 males and 17 females in the cohort (median age 36 years, range 16–69y), including 9 with HIV disease and 2 organ-transplant recipients. Majority of patients (66%) had St Jude stage III/IV disease. The median increase in serum LDH level relative to normal (adjusted LDH) was 1.4 (range 1–65). Patients were treated with a combination of CNS-directed and systemic chemotherapy comprising of a pre-phase [fractionated (F_r) cyclophosphamide and prednisolone], followed by a possible total of 6 cycles of alternating F_r ifosfamide, dexamethasone, vincristine, cytarabine and etoposide [Cycle A], with F_r cyclophosphamide, dexamethasone, vincristine and adriamycin [Cycle B] as outlined by the German BFM paediatric protocols. Patients received a 24h intravenous infusion of MTX on d1 of each cycle of treatment. Based on the mean MTX dose administered per cycle, patients were stratified into three dosage groups: low (<1gm/m², n=4), intermediate (1–1.5g/m², n=24) or high (>1.5–3g/m², n=34). There were 3 toxic deaths, disease was refractory in 8 patients and 9 experienced disease relapse. Durable complete responses following BFM were observed in 46/66 (70%) patients. A significantly lower proportion of patients receiving high-dose MTX (17%) experienced treatment failure compared to 45% and 50% in the intermediate and low-dose groups respectively (Fisher’s Exact p=0.01). Risk stratification on the basis of pre-treatment stage and bulk of disease, adjusted LDH and ECOG score was however unable to identify patients who may benefit from intensifying MTX dosage. These data thus uniquely highlight the impact of MTX dose in influencing outcomes in adult BL as well as the need for novel biological markers to identify patients requiring additional therapeutic strategies.