HIGH-DOSE METHOTREXATE IN CHILDHOOD ALL

An event-free survival is currently achieved in 70-80% of children diagnosed with acute lymphocytic leukemia (ALL). A decline in the long-term sequalae from therapy is a challenge at present. Due to the high incidence of central nervous system (CNS) relapse in ALL patients, cranial irradiation was introduced as a prophylactic measure in the beginning of the 1970s. Cranial irradiation, however, may cause secondary malignancies in the CNS. In recent years neurotoxicities have been demonstrated to follow cranial irradiation in a large proportion of ALL patients. Because of these deleterious effects, most ALL protocols are limited to the combination intrathecal and intravenous methotrexate as the standard for CNS prophylaxis. In the 1970s, an intermediate dose was administered, while from the 1980s a high dose of methotrexate was combined with intrathecal methotrexate. The regular methotrexate dose of later years has been in the range of 5-8 g/m2. The intravenous methotrexate dose has actually varied from 2 to 33.6 g/m2. The highest dose, 33.6 g/m2, has been without intrathecal instillation. In a study from Norway, high-dose methotrexate (6-8 g/m2) was used, and only two (2.2%) of 89 ALL cases showed CNS relapse, both of reversible kind. In the United Kingdom, a randomized controlled study was started in 1990. Results published so far are based on a segment of cases characterized by standard risk and white blood cell count below 50 x 10(9); a 4% reduction in CNS relapse was found for high-dose methotrexate in comparison to those treated only with long-term intrathecal methotrexate. The use of methotrexate unalterably warrants some precautions. Rescue therapy with folinic acid is usually started 36 h after initiating the methotrexate infusion. Steps are also taken to secure adequate intake of fluids and alkalinization of the urine. Provided irradiation is avoided, neurotoxicities rarely occur. For regular high-dose methotrexate adverse effects mostly involve mucositis and myelosuppresion.