Of all patients with medulloblastoma, the treatment of children younger than 3 years of age is by far the most challenging and has the worst prognosis. Tumors in this population tend to be larger in size, often with early whole spinal cord dissemination, and the likelihood of total surgical resection of the tumor is less than in other populations. The current treatment is divided into three types: Jiang Tao, Department of Neurosurgery, Beijing Tiantan Hospital
(1): systemic chemotherapy combined with myeloablative, high-dose chemotherapy and radiotherapy if the tumor recurs; (2): systemic chemotherapy combined with local conformal radiotherapy; (3): systemic chemotherapy combined with intracerebroventricular chemotherapy . Because of the effects of radiation therapy on the growing brain and spinal cord, resulting in the possibility of severe impairment of memory, learning ability, personality, language function, hearing and other aspects of the child, all three means are used to delay or replace the use of radiotherapy as much as possible, and there is no definite conclusion about the timing, dose and range of application of radiotherapy.
Grill et al. used the first approach, using conventional chemotherapy as first-line therapy and high-dose chemotherapy, secondary surgery and radiotherapy for tumor recurrence or dissemination, with 5-year PFS and OS of 29% and 73% for children without tumor remnants or dissemination and 13% and 13% for children with dissemination, respectively. In the second approach, Ashley et al. used conformal radiotherapy (18-23.4 Gy in the whole cerebrospinal axis and 50.4-54 Gy in the tumor bed) to the posterior cranial fossa after induction chemotherapy in children without tumor dissemination, followed by maintenance chemotherapy in 74 children with a 4-year EFS and OS of 50% ± 6% and 69% ± 5.5%, respectively, with D/N type medulloblastoma had a 4-year EFS of 58% ± 8%. This author concluded that conformal radiotherapy of the posterior cranial fossa should be routinely used, but the need for radiotherapy if the child is of the D/N subtype is not clearly established.
In a third approach, Rutkowski et al. used intracerebroventricular administration of methotrexate instead of radiotherapy, and in this study, children in the general risk group had a 5-year EFS and OS of 82% ± 9% and 93% ± 6%, respectively, if the tumor was fully resected surgically, compared with 33% ± 14% and 38% ± 15% in children with dissemination. This author’s most recent report included 45 children with tumors that did not spread, whose 5-year EFS and OS were 57% ± 8% and 80% ± 6%, respectively; with the D/N type having a 5-year EFS and OS of 90% ± 7% and 100% ± 0%, respectively [32]. This author therefore considered that this approach could replace the use of radiotherapy if tumor dissemination did not occur, while in the presence of residual tumor and tumor dissemination, this author also favored high-dose chemotherapy. However, intracerebroventricular administration of methotrexate resulted in leukoencephalopathy in the majority of children and is the most important drawback of this therapy, which still requires long-term follow-up of the results.