Abstract: Objective To analyze and summarize the clinical characteristics of 4 cases of children medulloblastoma (MB) with disease progression during treatment, in order to improve the understanding of the disease, and accumulate valuable experience for future treatment.Methods The clinical manifestations, diagnosis and treatment of 4 children with MB were analyzed retrospectively from 2012 to 2014. Results Four patients (aged 3-11 years) were treated with tumor resection in our hospital. The tumor was 3.5-6.0 cm, and diagnosed as MB pathologically. Postoperative radiotherapy was performed for routine. Four patients were evaluated before chemotherapy, and all belong to grade Ⅳ, high-risk group. These 4 patients progressed at 7-9 cycles of chemotherapy with cerebrospinal dissemination. Case 1 and 2 had symptoms of intracranial hypertension and radiographic abnormalities, while case 3 and 4 only had radiographic abnormalities. There were no abnormal findings in cerebrospinal fluid cytology for all these 4 cases. In the follow-up treatment, case 1 was treated with second-line chemotherapy protocol, and was given intrathecal injection, the disease was then under control, but died of second progression after 6 months; Case 2 also shortened the chemotherapy interval, and add topotecan on the basis of second-line protocol, the disease was stable, and followed-up in outpatient; Case 3 and 4 were given prophylactic intrathecal therapy at the presence of radiographic abnormalities, follow-up with imaging examinations showed meningeal metastases were controlled. Case 3 died of intracranial primary tumor progression 3 months after chemotherapy withdrawal. Case 4 disease was stable and followed-up in outpatient.Conclusion Medulloblastoma is highly malignancy. Patients should get regular craniospinal irradiation after surgery, with vincristine every week during irradiation. Shorten the chemotherapy interval and regular monitoring of imaging and cerebrospinal fluid might prove prognosis, MRI sensitivity is better, intrathecal injection has a certain therapeutic effect on the cerebrospinal dissemination, especially in the absence of clinical manifestations, but only the cases with image changes, prophylactic intrathecal therapy can significantly improve the prognosis; On the basis of not increasing the dose of single drug, the combination of multiple drugs has certain effect on disease progression.

Key words: medulloblastoma, surgery, chemotherapy, radiotherapy, intrathecal injection of chemotherapy drugs